Just to clarify a couple of Bookworm's points:
Most single engine turboprops are classes (like Cessna SET or Pilatus SET) which means training is less organised, you don't need a TRTO, and an LPC only every 2 years.
All twin turboprops and turbojets are types and so require training at a TRTO and an annual LPC.
Differences training for VP props, retractable gear, turbochargers etc is valid indefinitely for all singles but not for twins.
For a twin, differences training is aircraft specific and so training on a PA34 does not qualify you to fly a C310. To remain current from a differences training perspective you must have flown the aircraft model within 2 years.
It's all in JAR-FCL (
www.jaa.nl) and LASORS on the CAA web site.