I just found out the hard way that the cameras only have a 90-day warranty.
They are not considered part of the home security system equipment, but an independent add-on (since they are unmonitored). They are also not part of any maintenance agreement you may have for your regular Comcast equipment.
We have had all cameras replaced several times within the last 2 years because the first set was not weatherproof (but they were installed by an Xfinity tech OUTSIDE, so you have to wonder), the second set was replaced soon after for corrosion problems on the connectors, and the third set just failed (the wireless card in the cameras died). Of course, this was after the 90-day warranty on the last set expired. I opted to replace only the most important one of the cameras at this time, because each new camera costs $140 plus $50 installation. For the record, it was the worst decision ever to go with XFinity Home. The home automation gadgets (e.g. light switches) all keep failing (after the warranty expires, of course) and some of the sensors that were added on had to be replaced already (the original take-over sensors are all okay, despite probably being quite old). We had to forego a lot of functions the old system had because XFinity Home did not support them, but a fast-talking salesman promised us the world at the time. In hindsight we should have stayed with the old monitoring company and put in a bunch of our own IP cameras instead.
It has also been very hard to get a tech appointment, though the last appointment was scheduled a day after I reported the trouble (slow time of year). Which was a welcome surprise, but that I was told I would now have to pay for a whole new set of cameras (we have 5) was extremely upsetting. Apparently the cameras we were sold are "weather-resistant", not "weather-proof". Be aware Comcast/XFinity will not assume any responsibility for the cameras being sub-standard for outdoor installations.