480 GTX temps?

My friend just bought a PNY reference 480gtx to replace a dying 5850, he got it for like $80, the card works great. Was stressed for a while with gaming and msi kombuster and seems to be working just fine. My only concern is that with the fan on auto it gets around 80c+. I know that the 400 and 500 series high end cards ran quite hot and that its normal. With the fan at 65-75% temps stay near 65c-70c while gaming. Assumning these temps are normal for the generation of the card, would continuous use while gaming at around these temps lower its life expectancy? Being a used gpu he would like to get the most use of it. I heard some say that replacing the thermal paste may lower temps by about 5-8c. I dont think getting an aftermarket cooler is worth getting, so would it be best to replace the paste? or just live with the noise and slightly higher heat that hes use to in his case?
 
well i ever time temps were monitored with the auto fan setting, bf3 was ran for about 30min, and i use msi afterburner to manually set the fans speed. Also 80c was an estimate as i forgot the exact readings just knew it was around there.