Car bonnet "bra"

[Simongoju]

Hi, just purchased a bonnet "bra" to protect against stone chips etc but I noticed on the instructions it says not to leave it on the car for more than 7 days.
Anyone got one/ had any experiance as to why this would be the case and is it not safe for the paintwork to be left on for prolonged period? Which if that is the case seems odd.
Thanks in advance 

[th3_f15t]

At a guess, 2 reasons;

1. The leather will not like being left outside in the varying weather
2. The moisture trapped under it may speed up rusting from any existing stone chips

It's probably just one of those things the manufacturer has to write to cover their ass.

[Kam88]

On my mates car he left it on for literally very long time and paint started to be slightly different shade took a lot of detailing and polishing to get it where it should be

[Marc-5-GTI]

Could be a warning about any grit/sand/dust getting under it and acting like sandpaper if it moves a bit?
I'm just guessing mind

[ed30sam123]

I would say a bonnet bra is more function than form. A lot of the show boys put them on when driving to the show then take them off when they get there. I don't think they were designed to be left on the car for a long time, also you never get to see that nice paint your protecting either if you have it covered all the time!