When I have to pay range time by the hour, I pre-load my 4 Glock mags to 17rds.
Most of the ranges in my area don't allow anthing but slow-fire. I have been thinking about getting in a league since that's now the only way I'll be able to practice drawing and firing.
When I am paying per hour, I don't rush my shots but I do everything else quickly like loading magazines - scoring targets and stuff like that.
A new range opened up by me with a flat fee for all-day firing. When I'm there I only load 5 rounds in a magazine, and I take my time loading them.
How many rounds I fire depends on a lot of things.
If I'm not shooting my Glock well, I'll start shooting my Ruger standard, concentrating on fundamentals. When I get a few good shot groups, I pick up the Glock again.
Earlier last year I had a bad day at the range, and determined to do well I just kept firing hoping to get through it. I'm not sure what I accomplished besides expending a lot of ammo.
Now if I'm not doing well, I try to relax, concentrate on the fundamentals - somethig I find myself saying a lot is "this is just like dry firing..." But if my shooting doesn't improve, I don't force it, I go back to my Ruger, shoot a few more targets and call it a day.
I did have an experience later last year where I was experiencing a problem, I was getting a flyer out of every five shots and I couldn't seem to get better consistency. But things turned around for me after maybe 20 minutes of shooting, I seemed to get in a zone and I was really happy with the groups I was creating. When I have a session like that, I'll definately put more rounds downrange because I'm having fun