Quite often when I do a distribution upgrade or hop, I begin to notice how loud my laptop fan is and wonder if it's the fault of the new system. Invariably it turns out that the heat sink is in need of a clean. I confirmed this today. Using my new install of Debian Wheezy, I was sure the laptop fan was loud, and wondered if it was Wheezy's fault. But booting back into Squeeze on the dual boot system, the fan was equally as loud. Time for a clean.
I think the period of version updates or distro hops has coincided with the build up of dust on the heat exchange fins on this laptop. The period for both seems to be about six months.
It only takes a surprisingly thin coating of dust on the copper heat exchange fins to get a laptop fan blowing hard almost constantly.