I keep it on cause it looks more cool, and less plain with it on ;D
I dont think you legally need to have it after you have purchased it , only manufacturers and sellers would need to keep it on for obvious reasons, it would also need to be kept on if it was used in a place of employment .
Diachi
Edit : It would also need to stay on if it was being used in a public demonstration.
I leave it on to keep units looking professional. And for my DIY’s, I put one (usually the same one recycled from the Aixiz module), although I never show the power ratings.
It depends. On my PPL I removed the sticker because it was placed on the air cooling ribs which looks weird imho. On my ebayser the sticker wasn't very adhesive so I removed it before it fell off by itself. On my other 2 lasers the warning labels are still in place.
If the laser cops ever pull you over with a class IIIb, it helps to have as many labels on it as you can. :-X I just found out the hard way by an FDA official this weekend in Florida...