How Long Can You Remain On Your Parents Auto Insurance? 
Depending on your state laws but in Montana as longs as you are living in the same household you need to be listed on the policy as a driver . When a policy gets issued most carriers the applications clearly states have you listed all drivers in the household or child who has regular access to the auto listed on the policy . The other oprion would be you be excluded from your parents policy but then if you do happen to drive their auto there is no coverage . 