Welcome!
Deer hides can be tricky to work with, largely because it is customary for us to hang carcasses "in skin" for a period of maturation before butchering. This often results in a lot of hair slip during the tanning process, if you're trying to do skin on hides.
Also, because deer hair is hollow and brittle, it can break when the hide is being worked.
However, for tanned leather without hair they're absolutely fine, apart from blood staining around bullet entry/exit points.
I have found that hides from carcasses hung for up to a week in proper chilled conditions are fine, but beyond that it can get a bit borderline.