We also feed free choice protein for the reason tlk mentioned above. All deer have access and don't have to compete for the limited amount thrown out by a timed feeder. We feed from Feb 1 through August, longer if it is really dry. Then we have fall food plots (really not plots as they total about 160 acres) that are primarily wheat that the deer utilize until it starts getting too mature and less tender in January/February.
We had a protein feeder for every 100 acres this past year, but the wildlife biologist said one for every 200 acres was sufficient. We just consolidated them to one for every 175 acres, to make filling them a little easier, or quicker I should say. As of last week, we have gone through about a ton per feed station since February, but anticipate the consumption rate will double from June on. We typically don't use more than 18% protein unless it is really dry and the natural range conditions are poor. Then we may bump it up to 20% or higher to help offset the lower quality natural food the deer are also consuming. Deer don't just eat your protein, they are almost constantly eating when they are on their feet moving from bedding area to water to food source, etc.
Our biologists confirmed that the only deer that typically benefit from more than 16% protein in decent range conditions are fawns. They need a little extra protein that first year when they are growing the most. I wish there was a way to have a kids table for the fawns only, but that ain't possible.
You are doing the right thing supplementing with protein. The mineral content is as important, if not more than the % of protein. For most of Texas, natural occurring mineral content in the plants deer eat is less than optimum for antler growth, so a good mineral/vitamin content is key. If you are feeding a timed feeder, I would follow stxranchman's advice and maybe even feed four or five times a night. I don't know how often you are at your place, but if you can experiment with the quantities you feed, you may be able to adjust your feed rate until you have just a little leftover which would indicate most deer are getting their fill. You would need to adjust periodically though as we get to the summer and range conditions usually deteriorate.