Do you mean, am I worried that he'll get run into the ground long-term, and become injury-prone? If that's your question, I guess my answer is not really, for a couple of reasons:
-- a pretty healthy percentage of his touches are receptions, and generally speaking I don't think *receiving* touches carry the same weight as actual carries. (On a typical carry between the tackles, an RB may get hit straight on several times; but on a reception the RB is in space and is less likely to take a beating.) I think the comparisons of Bell and Matt Forte are pretty spot on -- you'll notice Bell, for all of his focus, could still finish shy of 300 carries for the year. But like Forte he may be in that 70 - 90 reception range annually.
-- I don't think the current arrangement (Bell with no proven vet behind him) will last longer than this year. Clearly the Steelers brass wanted a reliable vet behind Bell when they went after Blount in FA; it simply didn't work out. I fully expect them to add some experience and talent behind him next year since they already tried this year.
Remember too that Bell is a fairly big back (230 maybe, even after the weight loss) that *can* take a pounding, but rarely needs to because he has good short-area quickness and doesn't take a ton of direct hits.
Having said all that, maybe Bell gets injured the very next game, who knows. But I don't think it will be because of excessive workload this year if he does...sometimes injuries just happen.