Should I ever factory reset my CenturyLink provided modem?

NO!

DO NOT factory reset the modem provided to you by CenturyLink  – doing so wipes out critical information needed for your modem to function properly and you will be charged for the cost of restoring this information

Factory resetting is different than power cycling your modem. Power cycling your modem (turning it off and then on again) is often a viable troubleshooting step.