Buy the Forever stamp; it doesn't have an "amount" on it and is good for as long as you have that stamp no matter what the price of stamps has gone to. Maybe I'll buy and "save" one for a particular date or particular bill in 2037 or something, LOL.

I still remember when stamps were 4 cents. That's how much they were when I would write my grandmother thank you notes for presents, birthday and Christmas, etc.