On Sunday, February 10, 2013 9:56:35 AM UTC-8, David Farber wrote:
This Toshiba Satellite A135-S4656 laptop was given to me with the complaint

that it shuts off after a few hours.

from your excellent description it sounds like you need to replace the fan along with cleaning any dust accumulation in the heatsink ... fans go bad from wear and there is no way to lubricate them back to being operational except for maybe a short period of time ... try to find an original replacement fan because most of generic replacements are junk and will not last.