Constant login

All of a sudden, in the last two weeks, I am having to login to XFinity 6 times a day even though I check the stay logged in chkbox.  I used to only have to login a half dozen times a year (or so rarely that I never had an issue.)  Now I am going crazy constantly having to login.  I am using FireFox but it is not the default browser.  What is going on?  What has changed in the last two weeks?