These things are pretty simple and straight-forward. Probably not using any more metal than necessary. If the back of the light assembly wasn't muddy, salty, etc., wouldn't worry about it. Probably won't splash up there.
Also, I'm not in a rust area but I would guess these things are pretty much rust proof.
Would guess they are are built about the same so just enjoy and have fun!
"Take nothing but memories,
leave nothing but 'light tread marks'."