Whether or not your license is expired, if you are at fault in an accident (e.g. driving negligently, or carelessly, like too fast for conditions) and cause property damage or injuries, you can be sued; if you are sued and lose any assets of yours are potentially at risk. Having adequate insurance--which requires having a valid license--is the best way to protect yourself, since your insurer will pay any jugments (or award) against you, at least up to the limits of the insurance you bought.