The thermal paste in the AlBooks is reminiscent of concrete sludge: it's thick and gray and kind of grainy. If you start having problems (crashes, etc) with your machine, you might want to see if it's dried out or not. The AlBooks have tighter tolerances than the TiBooks with their thick thermal pads, so you might just be able to replace the sludge with Arctic Silver or something similar. While you're in there, blow out the dust and stuff with canned air.

If new heat compound doesn't help, maybe see if a good PC shop has some thermal pads to help bridge whatever gap may be between the processor/GPU and the heat sink. Also, make sure that the screws on the logic board are snug: time and heat can loosen them, especially if they weren't put in right to begin with.