Ahhh, you have opened the proverbial can of worms that has been debated "ad nauseum" on the big board at miata.net. I assume you refer to the vinyl cover as opposed to the clear plastic wrap. The naysayers claim that using a bra for extended periods of time will result in discoloration of paint, ie the paint not covered by the bra will tend to fade while the paint covered by the bra will not. They also claim that moisture trapped under the bra, regardless of how breathable the cover is supposed to be, will cause discoloration of the paint. Some suggest that just forget about a bra. If the front end picks up chips, etc, just have it repainted. Of course, they seem to forget that if the paint under the bra is permanently discolored, you can also have it repainted. I had a bra on my NA ('93) and used it extensively, leaving it on the car for long periods of time.in all weather conditions, rain, sun, etc. There was some discoloration of the paint under the bra. However, that was take care of with a good cleaner/wax. There was also a line of very faint indentations in the paint caused by the top seam of the bra being buffeted against the paint at high speed. They don't fit as tight as the ads claim. I also have a bra, with mirror covers for my NB ('04). I initially used it only for long trips and never had a problem..Admittedly, the NB began as a weekend toy, only in relatively mild weather; no cold temperatures (summer only performance tires). I also kept the car in a garage when not being driven. Now that I'm retired (since 2013) and have high performance all-weather tires, the NB has become my daily driver, using the bra only for long trips (over a few hundred miles). It still sits in the garage when I'm not using it. Ideally, I would go for the plastic wrap, installed by a professional. However, that can be expensive. I have considered it for the NB. However there are some nicks and chips that would have to be taken care of first. My suggestion: try it and see what happens. Just be aware of potential problems. i would wax the front end good prior to the first installation. Also remove it periodically to inspect the paint, particularly after driving in the rain to make sure everything dries out before re-installing it. Finally, current bras may be of better material and "more" breathable than the two I used. Good luck.
Del Val Miata Club