I have been in my stand anywhere from 30 min. before light and right at daylight and I found no difference in encountering animals. Bottom line, if deer are near your stand when you walk in you will blow them out in the dark too.
usually 45 min before first light but one time a buck I wanted would come into a field at 2 or 3am and stay in that field till day light, there was literally no way to get in there without spooking him so one morning I got in the stand at 1 am and got him that morning. I wouldn't do it again unless he would go in the record books.
Settled in at least an hour and a half before sunrise if not sooner. You can never be to early but a min to late may make a big difference. Just ask anyone who has ever missed a flight on a plane.
One of my brothers friends always spooked a buck he was after. One day he got into his stand at 3am and come legal time the buck was right there under his stand. Many times I have seen deer strolling under my stand at 5 ft if it wasn't for the light colored rocks I'd never have seen them. It told me to get further off the field.
I get in stand at least an hour before 1st light or I try not to go at all. Don't like to blow up my spots. There is one spot that I've gotten in stand 2-3 hours before first light because the deer like to eat the last hour or so of darkness over there a lot.
Saterday morning I was in my stand by 5:35, didn't get light enough to shoot till after 6:10.
Got to take my time and not sweat, and enjoy the peaceful morning in the stand in the dark for a while without worrying about seeing deer and making a shot.