Suddenly my WAN IP lease time is only 2 hours

I have an ASUS RT-AC86U Router and NETGEAR CM1000 Modem.  Nothing was change on my end when suddenly a few days ago I lost internet.  After a few power cycles and waiting an hour or so, my internet came back up.  However, I started intermittently losing internet.

After doing some digging, the only thing I noticed was that my WAN IP lease time was always 2 hours or less.  This stood out to me because I know it used to be a 7-day lease.  A few hours is really short, and any failure to renew in that time will result in a loss of internet.

Looking over my WAN settings on the router, I came across a "DHCP query frequency" setting which was set to the default mode of aggressive.  However, a new mode called "continuous" was released in an Asus firmware update a year or two ago.  I changed my settings to use this new mode and now my DHCP renewal seems to be successful every time within the two-hour window.  Still, this seems like a Band-Aid fix and the real issue is the fact that Xfinity is only issuing me a 2-hour lease.

Any ideas?  What controls how long a WAN IP is leased for?  I would imagine that it is tied to the MAC address of my router but everyone I chatted with said that Xfinity only needs the MAC of the modem, not the router.  I chatted with a few agents but nobody had any answers, and my modem has already been reset several times.  The only thing I can think of is to get a static WAN IP instead.