Did a full clean out of my laptop for the first time since purchase. Disassembled the chassis, removed the cooling fan, got out the air compressor to give everything a blow out, scraped off the old thermal paste and replaced it.
Everything seems OK so far, so it looks like nothing is damaged. The unit doesn't sound particularly different to before, except there was quite a bit of dust present when the fan was removed initially.
Also, I'm starting to wonder whether my unit was some sort of refurb or factory second or something... because I discovered one chassis screw is missing, one of the chassis latches was already weakened and there's quite a bit of duct tape on the inside. How the hell has it worked for more than 3 years now is a real mystery......