Your FAA Remote Pilot Certificate has a 24 calendar month shelf life — which means that you’ll need to complete a recurrent knowledge training course to maintain your status as a certificated sUAS pilot to operate under Part 107.
There is no “grace” period — meaning once you go beyond the 24 calendar month period you’re grounded and no longer legal to fly under Part 107 until you complete the online recurrent training course.
The FAA has not stipulated a number of days prior to your currency expiring when you need to complete the recurrent training course or imposed penalties for those who let their currency expire. So, if your currency has expired you’re no longer legal to fly under Part 107 until you complete the online recurrent training course.
For more information on completing the recurrent training course check out our guide, How to Renew Your FAA Remote Pilot Currency.