2008 toyota camry alternator

I have a friend who prematurely wore out his 100amp alternator after one year...running accessories and a stereo system off the oem battery and alternator.  The battery was replaced once already and now the alternator quit. He has decided to go with an aftermarket higher amp alternator that puts out a max of 180 amps. Granted it will never probably draw more than 150amps out of it..is this a good idea to do or is it risky to the vehicle wiring system and car itself? The alternator fuse is 120amps.  The dealer is not gonna cover the alternator under warranty because of the above mentioned. I am somewhat skeptical that his alternator wore out due to his stereo and amp. any input would be appreciated.

Highly unlikely, I would suggest a higher rated fuse and a higher amperage battery if you're taking this route. You might want to look at a split charge system with the second battery powering amps etc., keeping to the OEM battery and alternator.