my hypothesis on the "ylod" problem is, that the thermal paste Sony used for their first models was shit .. it loses too much viscosity when warmed and therefore slowly flows from the processors ,killing the effectiveness of the PS3s cooling system
ylod happens if the processor pins or the main board is damaged due to overheating
when I exchanged the paste in my launch PS3 it was in a horrible state and after I did the PS3 was as quiet again as when I bought it