30 minutes is MORE than enough. I have on occasion intentionally waited until it was the grey of dawn before slipping in, simply because of the situation. Every stand is different. But really, if you slip in quietly, climb, sit down and sit still, 15 or 20 minutes is enough. 1 1/2-2 hours does NOTHING to increase your odds really. In fact, you're half worn out from sitting before you can even see to shoot. It'll probably make you antsyier when you should be sitting still and getting in the hunt mode. 30 minutes the deer are far enough away from your stand to not see or hear you go in if you plan it right and don't arrive with flashing lights and banging and clattering. Why beat yourself up when you can't shoot before light anyway.
You really need more than one spot.