I do not know of any way within the OBi itself to schedule a reboot.
I have a Linux server on my home network, so I just use a cron entry that every day does:
curl --digest -u "$ADMIN:$PASSW" -s http://$OBI/rebootgetconfig.htm
That reboot seemed mandatory for my previous OBi110. Probably only every 2-3 days, but every day didn't hurt. I've just switched to an OBi202 and did the reboot for a few days, but I turned it off yesterday just to see if/how long it works OK.