Essex?....we're gonna have to ride one of these days. I PM you when it gets a bit warmer out.
Anyway, I rode with it for a year (about 3000 miles) before I took it off to paint it black. When I took it down I barely had any grime at all. I just wiped it off with a papertowel and spraypainted it. If you think about it, the way the tire is moving it releases dirt downward at the top of the battery bracket, not really the bottom part. Ive gotten caught in some really bad rainstorms and never had a problem either. Some guys on here added a fender piece to the lower part, but I personally think its not needed and takes away from the barebones idea. I think its been about 2 years now since I first installed it and about 7000 miles.