Keith, how are you cleaning your face shield between applications? I normally use Plexus every couple of hours on rural rides. Doesn't soumd like that would be good for the raincoat.
It wouldn't be good for the raincoat. My spray cleaner also tends to eat away at the raincoat. The difference is that I find I'm using the spray cleaner much less often now. Once the Raincoat has been applied, I have found that I get good results by just cleaning the visor with a clean cloth and NOT USING the spray cleaner. That seems to leave the Raincoat intact. I have a large stash of 100% cotton cloth diapers I picked up at a car show. They work awesome as cleaning and polish rags. Instead of using the spray cleaner every day, I'm down to using it about once a week.......and even then it is just a very light spritz intsead of the heavy application I used to use.
A normal routine for me in the morning is to just grab my trusty rag and clean my visor. If there are some stubborn spots or smears, I'll give it a very light spritz of cleaner and it works out great. I can tell when the Raincoat is starting to wear off because the bugs really start to stick and I get left with water spots on my visor. When that happens, I spend a few minutes and reapply it. I have found that it tends to last me about 2 weeks at a shot, which translates into about 1200 miles of commuting for me.
The biggest help to me was to lay off the spray cleaner. A good clean rag does the trick just fine.