" Is this a real serious issue? "
1. Not really. All fans in all devices do the same thing. A laptop is not unique in this respect.
2. A wish. It would have been nice that computer makers would have a yearly "maintenance you do yourself plan & guide". It's just wishful thinking...
Few few weeks ago, I happened to turn my notebook upside down and I found out that dusts are accumulated at the opening of the bottom exhaust vents. From this, I surmised that the bottom exhaust vents suck in air from outside and the side and back exhaust vents let out hot air from the inside. Probably, these dusts are dusts on my desk sucked in by the fan. If this is true, then over time these dusts will accumulate on the notebook components, thereby causing potential damage in the future. Namely, with dust accumulated, the notebook cooling might become less effective or air flow might become blocked. Is this a real serious issue?