How long before a lapse in insurance will affect you by the state imposing such penalties as a suspended license and/or suspended registration will depend upon the state laws in which you live. The penalty for a lapse in auto insurance varies depending on what state you reside and have your vehicle registered in. Typically, any gap in car insurance will cause the state to impose a penalty on you.
For example, in New York State any amount of time that your vehicle is registered but not insured can cause a lapse in your insurance coverage and the suspension of your registration. NYS DMV lists several situations in which a lapse in insurance coverage can occur. One is if there is time between your insurance being cancelled and the effective date that you begin new insurance and thus do not have acceptable proof of continual auto insurance coverage. If the lapse is over 90 days a NY license would be suspended.
Some states match registration information to information provided by insurance companies and when they find a lapse then penalties are handed down to the car owner.
Now in many states, including NY and Georgia, laws require insurance companies to notify the DMV electronically every time you obtain auto insurance and/or whenever your coverage has ended. Once this information has been received, if the DMV finds that there was a lapse in coverage generally they are the ones to send out the penalty notification to you.
In these states your license would be suspended rather quickly since the state is informed almost immediately by the insurer once your insurance has lapsed or been canceled and the state does not see a new policy started with a new insurance provider. To find out how long you would have in your state if you stopped paying on your insurance before your would have penalties placed on you, such as a license suspension, check with your local Department of Motor Vehicles.