my modem frequently goes offline for several seconds to minutes in the early morning

In the Seattle area, my Xfinity modem will go offline about once per week, usually between 12AM and 2AM. I am very confident the issue is upstream of my modem, not internal to my home network. These outages are generally brief, between five seconds and ten minutes, but that's long enough to be disruptive to multiplayer games. The outages always start at an exact multiple of 5 minutes, so e.g. 12:35:00 or 2:10:00, so it seems to be a planned maintenance of some kind.

I understand that maintenance is sometimes required, but why is it so frequent? I would expect maybe a few times per year, not weekly. And is there any way to be notified in advance or get a schedule of planned equipment reboots that affect my connection? That way at least I can plan for it so I don't get disconnected while piloting a helicopter full of my teammates.