As long as you think you won't bump one going in, the time on stand really doesn't matter IMO. I've had deer come in 10 minutes after taking the stand, so what does it matter how long you'll actually sit? If you have them patterned and know they'll probably be there about the time you're going on stand (e.g. entering a crop field or food plot), then I wouldn't risk it. It really all depends on your knowledge of that stand.