Most of the time the flash doesnt spook them enough to cause them to stop using the area, I get pics of alot of mature bucks each year and usually get pics of each one multiple times. Infact most of my cams are within bow range of my stands and if I thought that the cams flash spooked them I wouldnt have them anywhere near my stand locations.
In my opinion in most cases its not the flash or the camera but human scent
that causes a particular buck to stop visiting a camera site as a result of the cams owner checking it too often. I only check mine once every 4-6 weeks. Pike