Four timing belts; something is wearing them out

I have a 2001 Camry, 4cyl. I take good care of it. I have the regular maint done. The first timing belt I had replaced at 80K; then it stretched (I noticed unusual noises)and I had it checked, I was told it was defective after only 20k, had a new one installed; then I heard the noise again after about 20K more miles. It was going bad again. I had another one installed. The mechanic said something isn’t working right for this to to keep happening, but could not find the cause. Pully? The engine is making “the noise” again, so I have a feeling it’s the timing belt again. Any ideas? My car has 185K miles on it now, but like I said, this is the 4th timing belt and water pump.

An unusual noise does not mean a stretched belt. It is very difficult for a timing belt to stretch at all.
An unusual noise could be either a belt that is too tight, rough bearing in a belt tensioner or idler, etc.

Have the idler and tensioner pulleys been replaced?

belt tensioner or cam bearing(s) messed up.