When your plants stop stretching somewhere between day 35-42,throw on the 600..Temperature wise,you don't want too drastic of a swing consistently for example say 75-80°F in the daytime which is perfect but then a drop to say 60°F or below for a week or more not ideal..lights off personally I'd say 65°F-70°F is decent then lights on anywhere from 75°F-80°F if you can maintain it..I mean if the temp creeps a little over 80 sometimes but nothing too drastic and you have plenty of air exchange and circulation you'll be good..Dial in your temps and read your leaves..They will tell you more than anyone on this site can.Leaves folding like a taco or serrated edges lifting up are some stress indicators.
Good luck