Infinite levelling is possible
after the main game is over, when you can continue playing in the Battlefields indefinitely. During the game itself, it is very unlikely you will get much above level 40, I suspect, and I finished well below that.
I was level 29 at the end of the game, though I generally ignored most of the Battlefields after Act 2. I completed them in Act One, did roughly half in Act 2, then got bored with them <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
