CPU's overclocking ability can change over time aswell. Probably more so than the TIM joint issue. Also using the same CPU still tells us nothing more than others tests as the results are only good for that CPU.
Also I refuse to remove the IHS even on my $60 Sempron. I get what I get with what I got. This from a person using the stock AMD all aluminum heat sink though with no need to change it.
My system runs great as is.