Preventative maintenance? Your review mentions nothing about what this means. Comcast is a service. You shouldnt have to do a thing to keep their network running.
When I moved into my new place I had Comcast replace all the wiring to 3 Rooms and had them replace the drop from the pole. It was all done at no charge to me and I never had a problem with there service. Also a had a sub contractor here to add another room which had a long run about 30 feet and he was here 4 hrs and I only got charged 30.00 dollars and that was a couple of months after the original install. I'm very satisfied with Comcast and have Verizon Fios in my area and don't even give them the time of day. Its funny my friend has Fios and only has a g router when I get an n router.