After speaking with Geico, their "suggestion" was that even if you have a "student" who lives away from home (without a car), if their
permanent address is yours, and they use your vehicles when home, they
should be on your policy (as they are considered residing at your address). When pressed about the "should", his comment was that if they are an immediate family member (same last name and address) then it
could become an issue if an accident were to occur and a named insured was not in the vehicle. His "suggestion" was to keep them on the policy as either Deployed Military (AD) or Occasional Driver (ROTC or civilian driver) to protect yourself legally. I think maybe Florida is trouble as far as auto insurance because of all the fraud and staged accidents and lawsuits (we have "accident" attorneys on every block

). My wife and I determined it was more cost effective to just keep them on our policy and pay the reduced costs than in the worst case having to fight the insurer with or hire an attorney if something happened and Geico refused coverage.
The agent did say, that IF your child (any age) had a different "permanent" address that they would then be considered a guest and be covered under our insurance (ie: their DL showed a different state or physical address).
We have friends who got into the situation here where their insurer refused coverage because of an uninsured motorist (not in the family) and ended up having to fix their vehicles themselves. Had they been unfortunate enough to have their child "cause" the accident, the costs may have been astronomical.
I am not doubting
@justdoit19 or
@jebdad, but I would get any coverages for children studying away but using your address in writing or indicated on your policy, JMHO.