Postage

The Forever Stamp. An idea whose time has come. I'm not sure this is worth writing home about, so you might want to write home about something else, but for years I've thought it should work like this. Once you've paid the cost of mailing a letter, you should be able to do the actual mailing of it any time, today or in fifty years regardless of how much rates rise, because you paid full price when you bought the stamp.

It doesn't take much, does it? Now I'm happy.