timppu: Are you sure the thermal paste replacement is really needed, on a laptop? At least if I recall reading the instructions for e.g. Lenovo ThinkPad T400 fan replacement, I don't think they mentioned anything about having to apply thermal paste anywhere. The fan seemed to be a normal FRU that you can replace at will.

The first thing of course is to google for the hardware maintenance manual for your laptop, it should tell the needed maintenance steps, also when replacing FRUs.

timppu: Hmm, I've yet to have a laptop power adaptor die like that, even from the oldest laptops I have. One adaptor died, but it was a mechanical failure (the cord became broken/loose, I had apparently twisted it to the wrong direction when I disconnected it and packed away, all those years). Those adaptors have mostly been charging 24/7, at my work for example.

I personally don't see any reason not to have the laptop power adaptor plugged in all the time. Constantly plugging it in and out probably kills it mechanically faster than keeping it connected all the time ever could, and it is probably the easiest component of a laptop to replace anyway. :)