I assign nicknames to most girls I meet because I normally completely forget about them when they're out of sight. Outside of a rare few, I really don't bother thinking about them, so I just pick out a few features about them, and pick out a nickname so I'm reminded of who I'm even talking to.

Before I started doing that, it made things really awkward when I'd run into girl I had slept with a week or so later.

Also, I have no idea how many girls I've been with. Nor do I remember when I stopped caring enough to bother keeping count.