it is a half hour after sunset which is dark.

I think it depends on your area...but most of the time, I would say you are doing more harm then good. Now, you never know, one day a deer could come by and you could nail em', thats why anytime is good time, but I think I would look at the averages and that is that you are probably bumping more deer then the probability of seeing something, save the spot for the weekend!

You bet. Especially if you can slip in fairly quiet. The last 30 minutes of the day is the best hunting of the day. I killed a doe just a couple of weeks ago after being in the stand no more than 10 minutes. I got in the blind and was clipping some twigs that were bothering me and looked up and there stood a doe.