From what I have read and seen... Variation is the killer... 78 Degrees is good 82 is good but only a variation of about 2 degrees either way is tolerated... Once you acclimate something to a temperature, you've set a standard. Stick to it...
So... in short, if your target is 82, don't let it vary more than 80-84. 2 degrees either way is the tolerance... Again, from what I have read...
Personally, I run 80 as a standard and hold 80-82.