It is all a bit confusing and requires careful attention to stay on top of it all.
Many of us have to keep an eye on different expirey dates for 7 or even more ratings:
SEP
MEP
Instrument rating
Instructor rating
CPL licence
RT licence
(How many people realise the RT licence can run out? I know a guy who's RT licence ran out, and another whose PPL ran out before his SEP and he carried on flying for several months in blissful ignornance)
and lets not forget medicals...