Not really true, I have a couple 303's going on 3 years and the only reason the spot looked bad on one of mine was when I tried to clean it even though it was fine..Don't touch something if it ain't broke..All lasers lenses "tend to get dirty".
Roby, cheap and all,, these 303's aren't to bad. Alien Laser ran one 5 minutes straight with no issues and even dunked one in water and it still worked. "Yes" the water clogged the lens but still. "Don't try this by the way":can:
You must be doing something wrong to being having the same issue's??
The cans of compressed air will leave some foam type of spots.
Define the spots? Are you sure you don't have the "star" lens cap on?