I agree with Footbag. I kept mine at 81 for the longest (9 months)since it would spike to 81 during the peak hours of the day. Last couple of weeks (due to ventilation improvements), I have reduced the temp down to 78. The main thing is (as Footbad stated), keep it constant. At both ranges, I was able to not fluxuate even 1 degree.
Good Luck,
Jeremy