I went to the Apple Store and made it quite clear that I wasn't happy with the battery life in my then 1.75 y/o phone. The "genius" ran some tests, told me the battery was fine and then instructed me to turn off features in an effort to extend its life.
Does this strike you as good service? I would've been more than happy to buy a new battery had it been offered but was left unaware that it was even an option. My feeling is that Apple doesn't publicise this, preferring instead to "encourage" people to buy new phones when the battery is no longer up to scratch.
Now I know I'll go and get a new battery for my 2-year old 5s, that should give it a bit of a fresh lease on life. Thanks for the tip.