Like a lot of things in life, it depends. Mostly on how hard and/or often you brake.
If anyone has ever mentioned actually seeing your brakes glow, covers are definitely a no. If the covers are metal they can withstand hotter temps and of course plastics won’t. Probably obvious, but if you go to the track at all, probably don’t want to do covers.
The harder or more often you brake, the less you want interfering with their ability to cool.
edit:even if covers don’t melt right away, they will still suffer “fatigue” from the heat cycles (they will be affected by the heat coming off the brakes after all). When they fail depends, again, on braking situations. They might last longer than the car or fail tomorrow.
So, if you only rely on regen braking… go for it, I guess.
Dirt and stuff isn’t really avoidable, just cleaning the car once in a while should be enough to deal with that (or immediately after if you’ve gone knee deep in mud or standing water with debris or something).
Personally, I’m not a fan of brake covers. I’m debating taking off the ones that came with my MYP. If I had a bit more confidence, I might even go paint the brakes black (don’t really care for red brakes either).