Victor Manta wrote: A stamp collector from GB asked me some time ago from which date are the Swiss stamps valid for postage. I didn't know exactly and asked recently at the nearest post office. The answer was that the Swiss stamps are generally valid since 1960, with the exception of stamps sold at an additional premium, which are valid since 1964. This makes 40 years of validity for most of Swiss stamps.
I wonder what is the postage validity of stamps in other countries. And a follow-up question: which should be in your opinion the minimal duration of validity for postal stamps? Posted on RCSD the 10/22/99.

Edward Stamm: Only 40 years of validity of postage stamps doesn't sound like a good idea.  I have at times used (US) stamps well over 100 years old on mail (they were mint, but had major flaws that made them virtually worthless).    I would think that the postal administration would have to give some valid reason for this limitation.  In the US, you can't use stamps that were issued before 1865 on mail... not because of the length of time, but because stamps issued before that date were de-monitized due to the American Civil War.  That's a pretty good reason.  (Of course, who would want to use a pre-1865 stamp for postage anyway??!!)

A.M. Heindorff. In Denmark all stamps issued since 1st July 1933 are still valid for postage. Although all stamps with surface value lower than 0,25 kr. can no longer be bought at post offices, they are still valid for postage, giving a total length of validity of 66 years for most Danish stamps !!!!!

Helene Sarrazin: I find that question very interesting, as we all tend to admit that it works in other countries as in our own... and it doesn't most of the time :-)
In France, almost all stamps ever issued (since 1849) are still valid for postage, including the very rare 1 F Vermillion... ;-))
The rare exceptions are semi-postals issued before WW2, to the profit of Orphans and other Charity organizations, that had a limited postal value from their date of issue.
The other French stamps that have been demonetized (for obvious political reasons) are the PETAIN from the German Occupation in France.
If you want to put rare old classics on your mail, you can... but you must always remember that in 1960 occurred a currency reform, that exchanged 100 "old" francs (the value on stamps is always X F or X c.)for 1 "new" franc (the value on stamps always have a coma and 2 digitsafter it : 2,00). So, you must put 300 "old" francs to account for the standard letter rate (inside the country) of 3 FF.
If you REALLY want to use "Vermillions" on your mail, you can ! but you must put 300 of them... which, by the average value of 300 000 F each,makes a very expensive mail...
Generally, most people (except collectors, of course), don't know thatthey can use "old" mint stamps on mail... they only use the "new francs" stamps...
Perhaps something that has long been an advantage (a very long validity period) will suddenly become an enormous drawback (with the new Euro values  -V.M.), as the number of demonetized values will be over 3000 different stamps... Maybe other European collectors, from Euro-currency countries, could tell how it will work in their country...

Cary Finder: Of course, the stamps may be declared invalid by some postal clerks if they don't recognize them.
Someone told a story once about using a US stamp, Scott #906 (5 cent Chinese Resistance Issue of 1942) on a letter and being told by the post office clerk he turned it in to that Chinese stamps were not valid in the US mail.  Validity is sometimes in the eye of the postal clerk.

L & L Matthews: I live in Canada and the stamps here are valid right back to the issues ofQueen Victoria. Of course, most if not all of the stamps of that vintage seen used on modern mail most likely are faulty and not good for collections.

Ralph Ambrose:  I don't suppose that the United States is even considered in this discussion because  as far as I know US stamps are good forever, no matter how old.

Jim Lawler: Greetings Ralph, Not quite right.  When the Civil war got under way last century the "North" declared all stamps issued before the start of the war no longer valid for postage.  This was to devalue all the stamps in the "South's" hands.  So we have devalued stamps, at least once.

Edward Stamm: The United States Government demonitized all stamps on or about Jun 1, 1861.  A new set of stamps was issued by the US Government around August of 1861.  All stamps issued then and after are still valid for US postage.  Of course, the stamps issued by the Confederacy are not valid.

Richard Mostert: In The Netherlands all commems issued after 1976 are still valid plus thedefins of 1969-1976 (Queen Juliana). There is one curious exception, though. In the euro countries all current stamps will use valdity somewhere around 2002.

Arlene Sullivan: As far as I know, all Canadian stamps issued after 1859 (when Canada went to a dollar based currency) are still valid for postage.  I suspect that if you were foolish enough you could also use the Pence issues and sneak them by as an exercise. In addition, stamps of Newfoundland are also still valid for postage in Canada, so you could concievably frank a letter solely with stamps from Newfoundland, a "dead" stamp issuing entity, and have it delivered.
Aside from monetary upheaval, war, and other major crises, I see no reason why any arbitrary limit should be set on the validity of stamps.Can't you just see the post offices now - "Ooooo, we'll just make them valid for, oh, ten years, and then after that they'll have to buy new ones - bwahhaaahaaa!!!!!!!!....."  Way, way too tempting for the bean counters. Further to the validity of stamps in Canada, I suppose that issues of the Province of Canada (1859 - 1864) may have been made invalid when the Dominion of Canada was formed in 1867. 

Dave Joll: All stamps of New Zealand issued since 1967 (when the dollars and cents currency was adopted) are still valid for postage. Any remaining stamps in the sterling (pounds, shillings and pence) currency were invalidated about 1971. Previous to this, many older New Zealand stamps had been invalidated, as my father's grandmother found out in the 1960s when she used some old stamps found in her late husband's papers to post her Christmas cards - these stamps being the 2 1/2d "Wakitipu" errors of 1898, which had been demonetized many years earlier. Unfortunately I don't know if any of those surcharged Christmas card envelopes have survived, as they would make an interesting item!
In my opinion, stamps should be valid for either as long as the currency in which they are denominated remains in circulation, or the postal administration which issued them continues to exist. (As far as currency goes, three of the New Zealand sterling coins - the sixpence, shilling and florin - are still in circulation and interchangeable with the 5c, 10c and 20c coins respectively).

Ian Billings: When the USSR dissolved in 1991, its stamps remained on sale and valid in the 15 constituent republics which were then created.  Invalidity was
declared at different dates in these different countries.  Postal history of this period and area is fascinating!
What followed was a variety of stamps in different currencies: the earliest ones (it seems) were  accepted in any CIS country - eg Kyrgyzstan in Uzbekistan.  then different rates of inflation took hold, different postage rates were established, etc.
But the earliest stamps (issued in kopecks and roubles in 1992-3) are still valid and being used in some countries, notably Lithuania - where the actually currency has changed twice and the 'cost' and franking value of some stamps has also changed twice with no surcharge or overprint - and the central Asian countries.  What is not clear is what franking value a 50 kopeck stamp has now.
These are examples of stamps continuing to be valid long after one would have expected them to have been pulped, burnt, remaindered to collectors, or overprinted.  A fascinating area about which so little is known - but we're working on it!