my smart key dumbs down

I had two prior warnings: twice after turning off the engine, it wouldn't start again unless I put my smart key into the key slot, but then the problem disappeared and it worked again as a smart key. I assumed the fob battery was just getting weak... Today, however, with the smart key in my pocket, I couldn't start the car. So I tried changing the fob battery (I have done it successfully once before, so I know how to do it), but it still didn't work. I tried installing another new battery: still nothing. The little red light on the fob didn't go on when I pressed lock or unlock, the lock and unlock buttons on the fob didn't work either. I bought the car new in 2006 and have been using the same fob ever since. So...I decided it was time to switch to my spare smart key (2 keys, of course, came with the car), which worked fine. I went to my Toyota dealer, swallowed hard, and purchased a new fob for $260 plus $7 tax. I was originally quoted a price of $300 plus tax, which assumed one hour of labor ($220 fob+ $80 labor), but was charged less because they only needed half an hour of labor to program the new fob, maybe because I had the original metal tag with the number they needed to program a new fob? Anyway, the dealer went up in my estimation for charging me only for actual labor time. I kept the bad fob since I can use it as a non-smart key to start the engine.
I'm curious: has anyone else had a fob go bad? and if so, after how many years of use?