Well, first, Bow hunting is about how close you can get. the challenge! As for weight I personally would say min. 45, I could go down lower but ... I never worry about how far, I'm triying to see how "close" and undetected to make the shot!
It really is an individual choice, confidence in you equipment and skill, knowing your abilities!
Shoot as heavy, with control, Sharp broadhead, well tuned setup, and at a relaxed, unaware, animal, in the kill zone. Knowing the nature and characteristics of your game is just as important!