Look at your EASA Class 1 medical - it has respective Class 1 and Class 2 expiry dates. Once your Class 1 expires it will lapse to Class 2 privileges. The validity date of your medical depends on your age.
This assumes your Class 1 medical has not been suspended or cannot be renewed due to an existing medical condition. This may or may not impact your Class 2 privileges. You are best advised to discuss with your AME, that is what they are there for.