It's funny you bring up this topic, because I was just thinking of it last night. For the past few months I was fairly complacent, and sure, I was sleeping with girls, but it became a bit boring, and my approaches were half-assed. I knew that if my approach didn't go well, I could call girl x or girl y for a sure thing.
To make a long story short, I try to refresh my rotation of women every couple of months. It's just a personal preference, but unless I plan to make one of the girls an LTR, I like changing things up every now and again. I try not to stay complacent for too long. The benefit that I receive from having sex with the same girl after three months starts to diminish, so unless she's a keeper - I shake things up.
To make a long story short, I try to refresh my rotation of women every couple of months. It's just a personal preference, but unless I plan to make one of the girls an LTR, I like changing things up every now and again. I try not to stay complacent for too long. The benefit that I receive from having sex with the same girl after three months starts to diminish, so unless she's a keeper - I shake things up.