Seven years is a good life for a router. It sounds like it may be on the way out for you if it's rebooting spontaneously. Just take note, some types of traffic or devices have been known to cause routers to crash and reboot. See if you can narrow the problem down to a particular device, program, or activity on your network.
If all else fails, chat or call with Verizon. They should be more than happy to give you a new one.