06-26-2013 05:13 AM
I'm not certain there's an established policy on this. However I found recently that, having cancelled my old Comcast services and accounts over 18 months ago, I can still log in to comcast.net, and I still have an occasional email forwarded from my old ("cancelled") Comcast email accounts. I suspect this is pretty much standard ISP procedure, but I've never seen anything official on such a policy.
Remember you can always subscribe to online services specifically designed to maintain an email address even though you do not subscribe to the related ISP.
You might get better information if you asked Comcast/Comcast users about this. It's up to Comcast whether or not they disable your email account; Verizon has no control over it.