I rotate my EDC pretty regularly now. When I buy a new knife, I usually only carry it a week or two before I buy a new one and start carrying that. I'm really picky now, it doesn't take much to send me to Knives Plus or New Graham. "I don't like the blade finish" or "this would be perfect if the clip were just a little different" or even "this knife is too perfect, it doesn't have any quirks/ personality".
Sometimes I'll go back to some of my old favorites, but if I carry the same knife for more than a couple weeks now, it's noteworthy. I try to use all of my knives for at least a little while, so I have an appreciation of how well they work (or don't work). I'm not overly SD oriented, so developing muscle memory with a particular knife doesn't interest me much. I EDC mostly for fun, because I can, and I like sharp and shiny things. A waved Emerson is a pretty bad-ass letter opener at work! (I have my own office, so I can be as dorky as I want).