i do think they need light. if you want the best for your snake you should try to copy their natural habitat in their viv so in nature snakes have light so in the viv they should have light to. you can use a uva lamp for this (these one doesn't create heat) best is u put it on a timer 12 hours on 12 hours off
i was talking about a room with no natural lightIf you have your viv in a room with a window that gets natural light, that's more than enough.
i also put the uth on 24 hours sicle but u should use a thermostat. then you can put the light on a timer it's very easy and cheap, and you don't need to do aything about it anymore
the uth should cover 1/4 to 1/2 of the tank
I use a 60 watt on one end of the tank. I always turn it on and off every 12 hours. I would use only a UTH OR a light, because with both it may get too hot. My 60 watt keeps it around 85 degrees on the warm side and high 70's on the cool side. I've never had any problems with just the light.