Car insurance companies are already generally legally required to give notice in writing 30 days before cancelling your policy, even for material changes in risk.
You're the one proposing to change real world policies. I find it really interesting that I'm speaking directly from the libertarian playbook and the anti-insurance folks in the conversation are telling me to trust the government regulations. Especially when those very government regulations would be eviscerated by the proposed changes.
Let’s try to stick to the real world.