I think the bigger concern shouldn't be the amount of minutes that Rondo is playing, but whether or not he should be playing at all. Hamstring injuries can be tricky, if Rondo tries pushing himself when he's not 100%, he could end up out for a long time.
But if he's deemed good enough to go, I don't really see a problem with him playing a bunch of minutes. He's more susecptible to tightening up on the bench. Granted, 45 minutes would catch up to you night after night, and he can probably ride a stationary bike or something while he's out to stay loose, but as I said, I think the bigger question is whether he should be playing at all, not the # of minutes. But I have no idea the extent of Rondo's condition.