Absolutely Fed Up with Performance Degrading

running on HP Dv7t...4mb ram...nvidia gforce 320m...

I sometimes get days of use at 30fps or better... and then inexplicable dropouts in performance that make FS unplayable.

I think my setup should be perfectly adequate to run FS9. I've tweaked and re-tweaked settings to coax more fps out of it but I'm out of ideas...

Has anyone found a magic fix to insure long term good to high performance?