My Acer is a little over 7 years old. I've applied thermal paste twice and just did a complete reinstall of Windows Vista because... well, he's seven years old. I took him to school for a year and decided he was waaaaay too heavy so he became a home-laptop. He lives on a cooling pad (not plugged in, just slanted for nice viewing and air circulation). I haven't noticed any overheating issues because as soon as I do I check for dust and reapply paste if needed. So far that's always been the problem.
Honestly, I've found both Acers (mine and my parents) run fine with some TLC. Sure, I can't play games or do intensive computing but I don't really do either often enough to want something more expensive and powerful. IMHO, however, desktops are a lot less of a PITA to maintain, replace parts, run without burning something, etc.
I did have a horrible experience with an Asus eee 1005HA but this is an Acer thread...