Do your other devices stay connected ie: cell phones , tablets, streaming devices if you have any?
If so maybe you should just use the comcast router being you stated you have used the linksy for several years problem free. No routers last forever a number of tech sites even recommend replacing after a couple of years. I went through similar issues with my last cable company because they only provided new customers with a combo modem/router. I was going through routers every 2 years or so for many years. The first thing that started happening was the wi-fi signal would weaken and become spotty throughout the house, download speed would also decrease, and devices started losing the connection if they were not close to the router. The same happened whether inexpensive or expensive routers. My current cable provider supplies the combo modems which seem to only last the same maybe 2 years before I have to replace , it may be because we have a lot of devices connected all the time , (multiple laptops, tablets ,cell phones, tv's ,security cam's ,alarm system, etc.)
You more than likely have a bad New Comcast router ,that sometimes happens , you should not have to do all the techy stuff to get and maintain connection, simple reason is that I think I can safely say that more than 75 % of their customers have no understanding of ,Ip addresses, Mac addresses or how to configure router settings if they can even get into the setup.
Heck many can't even enter the passwords in their own devices. In my opinion I would just turn in that equipment and get another stating you keep having connectivity issues and want another. This way you do not have to wait for a service call and waste a large portion of your day waiting.
If your problem is not already solved I hope this helps.