The EASA PPL Licence has a lifetime validity.
Ratings within your licence, such as the Single Engine Piston (land) rating, may need revalidating or renewing in order to keep them valid.
A Single Engine Piston rating is valid for 2 years.
Anyone must have a valid and appropriate class or type rating in order to do any flying other than flying under instruction, skill tests or proficiency checks for the renewal of type or class ratings.
Holders of a pilot licence shall act as pilots of an aircraft only if they have a valid and appropriate class or type rating.
Pilots shall complete differences training or familiarisation in order to extend their privileges to another variant of aircraft within one class or type rating.
Differences training requires the acquisition of additional knowledge and training on an appropriate training device or the aircraft. i.e. it likely has a practical training element
Familiarisation training requires the acquisition of additional knowledge. i.e. knowledge can be acquired through study, not necessarily through training.