Genuine unused Forever stamps do not expire merely because postage rates change. Their value follows the current one-ounce First-Class Mail letter rate.
What remains valid
USPS generally accepts U. S. postage issued since 1860 unless a DMM rule makes it invalid. A rate increase does not require exchanging a valid unused Forever stamp.
What can make a stamp unusable
Already-used, counterfeit, damaged, defaced or improperly covered stamps are not equivalent to valid unused postage. Keep stamps dry, flat and attached to their backing until use.
One stamp does not cover every piece
Extra weight, nonmachinable shape, international mail, flats, packages and added services can require more postage or a different category.
No stock-up promise
This guide makes no personal-expert, inflation-hedge, wholesale-source or guaranteed-savings claim. Buy only the quantity you reasonably expect to use and verify the seller.
Sources and update note
Issue facts and current postal rules should be checked against the linked primary sources. Prices, inventory, services and policies can change.