Like Marty, I have tanks all over my farm even though I have two dams that hold water. Mine are all dug into drainage routes and fill up easily when we get an inch of rain. However last year and this year mother nature kept them dry for the most part. The ones I can drive to, I've been filling every 10 days or so this fall/winter.. They are 110 gallon tanks and the critters have been drinking them down to where they are half empty or more in that time frame. The water has been like a pile of survey corn. The deer flock to it.
I knew they got used but I've never put cameras on the tanks until this year. I wanted to see how much use they get in drought situations and what all came to them. I have had deer basically wait their turn until they could get to the water, with the line 8 deep. Bucks tended does to the tanks(watched that from the stand). Deer of all ages use them day and night and have given me some good pics to study. Bobcats, squirrels, coons, possums, birds, and deer are regular consumers.
The deer are a bit apprehensive about dropping their front legs into the tanks when they get low but will do so, with most going to their knees to reach the water when it gets that far down so I'm going to use the front end loader on the ones that are topographically set up that will allow me to dig out a side so they can reach it without having to get on their knees or put front feet in them when they get that low.
I am going to add two 330 gallon tanks this spring, one of which I will be able to plumb hose to and keep filled year round. Adding water to where you hunt if possible is IMO is a no brainer, even if you think you got plenty of water.