There's a certain level of comfort associated with carrying the same gun.
I used to definitely do the whole "If it's Tuesday, I must be carrying the Luger" thing. And I understand the desire, even if you're carrying concealed, to have something cool-looking or pretty on, whether anyone else can see it or not. If people weren't like that, they'd sell nothing but tighty-whities and granny panties in stores and Joe Boxer and Vickie's Secret would be long out of business.
I just don't do the CCW as fashion statement anymore. I haven't for a while. I change carry guns only marginally more frequently than the country changes presidential administrations. I sometimes miss the "Whatcha carryin' today?" easy conversation starter among fellow gun nuts ("Same gun I've been carrying since you've known me, why?") but maybe the time savings from not having to select a gun and holster in the morning is worth it.
I was reflecting on something similar regarding pocket knives in a recent conversation with Marko. I've got... well, dozens, at least, of pocket knives, ranging from fairly pedestrian CRKTs up through a Walter Brend/White Wolf auto that has appreciated to the point where I don't really want to carry it, and yet every day for months now has found me carrying the same Spyderco Delica with the "wave" opener. It's light, handy, has the handy "wave" opener, and I don't spend the time trying to figure out what's going in my pocket this morning: The same thing as yesterday, that's what.
I think it's time to admit to myself that I'm just a creature of habit. I may have all kinds of rationalizations for driving the same car for thirteen years, but maybe I just like knowing where the corners are.