It depends on what I have gone to the range to accomplish. Take last night for example. I had two tasks I wanted to finish. One was to sight in a new scope on my .22lr. When I had done that, I was finished. The total was just a few rounds to get the scope zeroed. My other task was to check out a new return spring on my pistol. When I make a change to my primary, I shoot at least 200 rounds through it. So last night I shot enough to satisfy myself that the spring will not fail on me.
My next tasks are to pattern my Mossberg and get a feel for where POI is in relation to POA. To do that should take no more than ten to fifteen shells at most.
Another purpose may be to test a new load. That would take anywhere from 30 to 100 rounds in a session, depending on the min-max spread of the load data.
So you see that each time I go I have a purpose in mind and will use whatever it takes to accomplish that purpose.
When liberty is taken away by force it can be restored by force. When it is relinquished voluntarily by default it can never be recovered. ~ Dorothy Thompson