It's all about stress on the motor.
The engine in the Camry makes like 98hp.
If you had it modded out to 175hp, it would die a quick death.
Just like if your taking a 235hp engine, and pushing it to 400hp, and it becomes "unreliable" suddenly.
Ok, so I know some 7M's have died due to rod knock, and that the 7M has/had a head gasket problem, mostly because of the low factory tourqe spec on the bolts. (52lbs is about 20lbs too low we have since found out.)
If you run your stock 7M with full oil, and 72lbs on the head bolts, they are very reliable. On stock boost that is. Heck, I'd say they are reliable at 10lbs of boost on a stock CT, stock HG and bolts to 72lbs, especially if you run 6 quarts of oil in the motor all the time. (About one quart high, but it's a good safety net oil wise, and your in no danger of having the oil whipped up by the crank at 6 quarts.)