Is it bad for a winch to not have tension on it at all times?

I have a winch on a trailer and load and unload things regularly. There is a battery to power the winch on the trailer and when plugged into the truck the battery gets charged. Afraid of running the battery down and overusing the winch I bring the slack back in and leave it for a while without any tension on it, I was wondering if it was fine to keep doing the way I am or should I always keep tension?