If it has been happening from the get-go I would try pressing DirecTV for a realignment. That's another problem with installs in inconvenient locations: the installers might not take the time necessary to get it aimed dead-on.
Simple fact that the better the dish is aligned, the less likely you are to have outages. 80's and 70's on a good day means many more outages than an install where high 90's is the norm.