Disadvantages in having a car in my name only?

I presume he is the beneficiary of your will, so if you die he will simply inherit the cars. He could sell all the extra vehicles and just keep one and have it transferred to his own name, or sell all of them and buy one newer car in his own name. In the meantime, if he is a named driver on the insurance policy, he could continue to drive during the life of the policy. In the country where I live, car insurance is mostly paid annually. When the renewal date comes up, I don't think he could continue to renew it under your name. The renewal policy needs our signature, and for him to sign yours would be a fraud which would render the insurance invalid. If he took the step of selling all the cars and getting one in his name, then he would get insurance for it in his name too.