Not so much engines going bang heavyd, more so turbo's blowing , breaking of blades in the turbo, and being blasted into the engine causing failure.
The engine overtime WILL at some stage give some form of stress failure, as it wasnt built to withstand these extra strains.
You are simply kidding yourself if you think that it will cope with all the additional power and torque, at some stage it will result in some sort of failure, whether it's tomorrow, or its much later in the cars life, hopefully when your not the owner of the car still.
My thoughts might not been agreed by all, but i feel, if you plan to keep your car, like Greeners has already said, the last thing I'd ever do is max the car out for little more benefit.
I sometimes worry about running stage 2, but I try to warm up and warm down the car when I use it.