William has an Airport Extreme router that disconnects 3-4 times a day. Leo says that's not unusual with routers. They're basically just a dumb computer that sometimes crashes. So he'll have to unplug and reboot it. If it continues after that, it indicates that the router is starting to fail and he'll need to replace it. He can also try rebooting his modem.
It also could be interference, and it's likely on the 2.4Ghz spectrum. If he has the ability to use 5Ghz, he should use that. He should also check for microwaves, cordless phones, and anything that could cause interference with the Wi-Fi.