^He pretty much stayed consistently the same age (thanks to makeup) for the run of TNG and the movies. And dying his hair white didn't affect his age. Plus,at one point (the episode in question escapes me) he did mention feeling hesitant about outliving his friends, making new friends, and outliving them too. That doesn't sound like the words of someone who thought he aged like a normal human.
I don't think Data aging and Data having a maximum life span are the same thing. Granted it may be strange having an android walking around that looks 900 years old...