I really can appreciate what RJF is saying. To me, shooting is a relaxing sport and I really enjoy just contemplating the day and my shooting while I'm 'thumb'ng' some in the mags. I've got 10+ 30rd AR mags so if I'm into blasting some 300+ rds in a sitting I've got that covered.
However, I've found that with my M1A (I got it a few years before my Mini) I take my lowly 5ea 20rd mags and shoot in a relaxing rhythm. If I'm in the mood to shoot more, then I leisurely load them up again. If I'm not, then I'm done. It's more about the 'getting into the rhythm and the mood' vs just sending them down range.
So, my 10ea 20rd Mini mags gives me a great number of rds to run through before I have to think about refilling them. Heck, no matter how many I shoot of any mag. When I'm done for the day, I always refill the mags at the range considering the shooting. Enjoying the outing and reveling in the freedom to enjoy a great sport and a great place to live.
The 'place' I get into when I shoot is fantastic the last dozen or so years. It's not about even hitting anything (however, I do well in the zone). Rather, it's that comfortable feeling of being one with the rifle and the event. I don't even notice I'm refilling my mags. It's just all about being in the moment, being into the shooting, enjoying the sights, sounds, and experience.
BTW, this sounds way, way to zen like for what it really is. I just enjoy the deep satisfaction of being outside with my firearms. Of being free to enjoy the moment. Of being with myself.