In the UK, engine life rules can be found in CAA CAP747 GR No 24 (it isn't an Airworthiness Directive and isn't issued by EASA):
http://www.caa.co.uk/docs/33/CAP747_Issue3_Nov2014.pdf
Lycoming recommend that the O-320-D3G used in the Warrior is overhauled at 2000 hours or 12 years whichever occurs first (Time Before Overhaul, TBO).
In the UK, pre-EASA, the calendar life wasn't enforced but the advent of EASA brought the UK into line with the rest of Europe.
If the aircraft is used for flying training or private hire etc, it can continue to be run 'on extension' which is to 20% past TBO - so that is an additional 400 hours or 2.4 years (2400hrs and/or 14.4 years).
At that point the engine must be overhauled unless it is used for private use only, the engine is then termed 'on condition'.
GR 24 rules include an annual or 100 hour check of cylinder compressions, monitoring or oil consumption.