1. The heatsinks collect some insulating dust or lint. This is not a defect, but what fans and heatsinks do.
2. Some laptops need a little heatsink help. The heatsink gets dislodged or lifts off a little. Not uncommon.
I have a Sharp Mebius laptop that I've only had for about a little over a year now. Recently, only after being on for an hour or two, the computer will overheat and shut down. I can feel the hot air being blown out by the fan from all ends, so I know the fans are working. I've tried using it on different surfaces and that didn't really help, though I wasn't sure that it would. This isn't an issue that ocurrs regularly, but I thought I'd ask for some help if it's out there.