So with convertibles, I’ve always wondered, how often do you have to clean bird crap off of your interior?
I've never cleaned bird crap off my interior. It's been on my back deck a couple of times. That's not to say that it's never landed inside the car, but not that I've noticed.
Mostly, bird crap hits your windshield when you're driving. I rarely see bird crap anywhere on my car from being parked somewhere, and the odds of it being on the interior are about half that. There's this fascination that non-convertible people have about birds crapping in open convertibles, as if that somehow attracts birds. When you see cars with bird crap all over them, it's from being parked outside of a garage, in a bird-prone space.
I've parked under trees and gotten a bunch of pine needles in the car. But that's not a good idea for any car, because of the pine sap. And a couple of times, many years ago, I left plastic-bodied cigar lighters in my center console, on sunny days. And at a certain time, sunlight would bounce off the metal shift-knob trim in such a way that it made the butane reservoir boil. They never exploded, but they just about doubled in size (and stopped working).