Stamps

Being a fairly wired (and wireless) kind of guy, I rarely send out snail mail. I use the web, email and IM whenever I can, and I use an online bill paying service. Hence, I rarely need stamps. I used to alway ask someone for a stamp, and inevitably they refuse the dollar I offer in exchange (lacking change but considering my time to go buy stamps more valuable).
But I finally got to where I have a small book of stamps in my wallet and another on my desk. Now the problem is that I use them rarely, and often have old stamps after the Post Office hikes rates.
Instead, The Post Office should issue stamps for first-class mail with some kind of code, rather than a price. Something like FC-1, -2, -3...etc., incremented each time new rates are effected. I think they already do something like this, but in addition, they should honor older uncanceled stamps as valid for first-class letter delivery, rather than for their face (or book) value. I mean, I paid for some number of first-class stamps, I should be able to use them without having to get extra stamps, just because I don't mail that often.
Now, I'm happy to have the stamp revert to it's monetary value when I combine it with other stamps. But they've gotten to use my money since I bought them, money that could otherwise be earning me interest. So, I figure they owe me the delivery of several first-class letters.