Your TR is valid for 5 years if after 12 months and you have no time on the a/c you will have to do another LST Licence SkillsTest before you can fly for an airline. But you do not have to do one every 12 months, if you are not flying.
If you are working you have do a
LST every 12 months. the LST is done in the sim, by a CAA of JAA examiner