^^^^ What Chris said ^^^^ Hagerty requires that every driver in the household that they will cover on the classic car have another car and insurance policy in force at the time; and they ask for proof. They do not want the car used as a daily driver. Other than that, no mileage restrictions. I was also impressed with the fact that they had no age restrictions. When my older son got his license, they had no problem adding him to the policy, once we showed that we had another car in the household that he was using as his daily driver.
One thing that does scare me a bit about Hagerty is that their default policy has very low liability levels, basically the state minimum. So, consider upping that, particularly if you have any other assets that you want to protect.
Keith