at cellshock i always ran the asus p5k3 deluxe boards at 1.7v nb voltage with a 80mm fan blowing on the mem and the stock heatsink.
i ran them like that for months... like 8 months i think?
and they didnt degrade at all...

then again, this was on open stands and not inside a case...
your nb temps sound really high considering you have a fan blowing on the heatsink
what case temp do you have?
is that fan on the nb blowing at full speed?