The modern +P rated airweight J-frames are quite tough. I shoot them quite a bit, and they do not loosen up or go out of time easily. I have over 3,000 rounds through one of them, and it has not had any problems. I shoot mostly standard pressure rounds, but I do shoot +P when I feel like it, and it does not cause any issues.
The older airweight guns are a different story. They have a reputation for cracking the frames right under where the barrel screws in. I would only shoot one with standard pressure ammo, and probably pretty sparingly. I would not shoot one on a very frequent basis like I do with a modern 642.