I have an LA135 and had read where others have had this issue as well...where the belt rubs a section out of the belt guard. Apparently it is a design flaw from what I understand.
I've run my 135 for about 7 hours, but at about 4 or so, I decided to give the deck a good once over and found that after only 4 hours, my belt guards did indeed have these areas rubbed away by the belt.
I figure that the damage is already done, and now that the grooves are worn, there's probably not much to worry about.