You may revoke your policy before it expires only when your policy allows it. When you cancel your policy, any premium refund will primarily be sent to you under a certain time frame.
Say that you've changed your viewpoint about purchasing insurance, most general insurance products offer a good minimum cooling-off period. It means you could indeed cancel your policy at any time without incurring any penalties or losing any of your premium payments.
At a certain point in time, at an appropriate juncture, you may renew your policy. The insurer should first notify you in writing that your policy will expire in a specified number of days before the expiration date. Also, it may agree to renew the insurance contract. Unless the insurer fails in doing so, the Insurance and Reinsurance Law of the United States treats the policy as continuing for another term unless you replace it.
If an insurer plans to cancel your insurance contract, it must provide you with formal and written notice of its intentions. After the minimum notice period, you receive the cancellation notice. Many insurers provide longer notice periods.