I have 3 knock-off vent covers that are plastic and simple screws through the plastic into the metal brackets set up (no nuts). Had them installed when we took delivery of the camper. Been up 3 years now and we've traveled quite a few thousand miles since ... quite a few thousand! All 3 are still up there, no problems at all. I think you are fine. Try it a while and see what happens.
I'm expecting after 5 years for the plastic to start getting brittle. This happened to our previous camper. We did not have covers, just the factory crank vent covers. About the 5th year of ownership the camper got hit by hail which busted out all 3 vents (plastic lids). We had them replaced no problem, but the plastic was extremely brittle and had no "give" any more. That's probably why the hail hitting them finally broke them out.
So, I'm expecting about the 5th to 6th year of ownership for these cheap-o-knock off brad vent covers to go brittle too. But if hail destroys these, I'm not out much. Simple to replace with just screws.
