I have comcast as well and went through what you are experiencing right now and it took them almost a year to fix it.
What my problem was, i was more than 11,000 feet away from the node.
What i did was take tracer routes for every site i could think of and take screen shots and complained my ass off !!!
Also got neighbors involved as well and finally after going through level 2 tech support , poof they added another node closer to my house.
I hate to give you bad news on the timing but hopefully Comcast has gotten there sheet together better and it will not take as long for you as it did for me.