aless85 - FCL.710(c) - The differences training shall be entered in the pilot's logbook or equivalent record and
signed by the instructor as appropriate.
RTN11 - Differences training is not required between different aircraft in the SEP class except where indicated in the
EASA Type Ratings and Licence Endorsement List . Scroll down to Table 10 and you will see exactly where differences training is required. The cut-off for MEP differences training is 2 years (see FCL.710(b))