I have two instruments I consider my "main" instruments. That's my Tele and my A/E. Someday I shall have to name them, but right now "my electric" and "my acoustic" uniquely identify them.
For instruments that are not my main instruments, I switch strings when they break. I changed strings on my fiddle once because, "Hey, I've never changed strings on a fiddle before", and once because "Hey, these Black Diamand fiddle strings just suck so much!" I once, several decades ago, put new strings on a bass, but never since, and I can't for the life of me recall if there was any breakage involved. Intellectually, I think that coated strings like Elixirs are a great idea for non-main instruments, since they'll last on instruments set aside for a while. Financially, I can't back that up.
I once saw that Nickel Creek were Elixir string endorsers. I noticed that Chris and Sean were named and interviewed, but Sara didn't. I wondered why. The I realized/remembered that the bow sticks to the strings, and that grabbing and letting go, we get vibrations. You gotta put a lot of rosin onto a new bow to make it work. The last things you want are slippery coated strings that won't grab the bow.
My Wednesday playing these days is all acoustic, being part of a worship band with two guitars, bass, grand piano and drums. Except, can you really call it "acoustic" playing when you're in a lead channel on your GT8? Anyway, the acoustic sound I dislike is the clanky, chimey new string sound and like it better when the strings settle in a bit. For the acoustic, I change all the strings when the G string breaks, because I figure that if I just swap out the G, it won't be too long before I've beaten the D string enough to break. If I had a bigger gear budget, I'd probably keep my acoustic string change regimen about the same.
For the Tele, things are different. When I had bridge cables on, I still bent, and now that I'm running with angel hair for strings, I just bend more, and the longer you keep strings on, the more elasticity they lose and the more they detune when you bend. I know that most heavy touring players swap guitar strings after every gig because the sweat and the gunk that builds up under the hot lights kills a string, and studio guys wanting to get a consistent bright tone have their strings changed every day or several times a day. I've never been that guy, but I could probably use changing strings more often than I do, which is "rarely". Certainly when it breaks. Mostly when they look grungy.
Looking at the pole to the right, I see that I am not alone in letting the strings stay on for a while. Is it an aesthetic choice or an economic choice? What strings do you like?