answer:Stamps do not expire. If you have one of the new “Forever Stamps”, then no matter what the rate goes up to, you can use the “forever stamp” by itself. So, if the rate goes up to $.50, and you have a “forever stamp” that you only paid $.41 for, you can still use it by itself (you don’t have to add $.09 worth of stamps to make the postage equal $.50). Back to your question. As long as they have not been used, in other words, they haven’t been stamped/postmarked by the USPS, then they are good to go. If you have a stamp from the 70s, then you just have to add stamps to make the postage equal at least $.41 if it’s just a normal letter. But, if they’re cool stamps from the 70s, why would you want to use them? If they are unused, then they might be collectible. Check ebay or something to see if they are worth more than the face value.