2 Years.
Compulsory Basic Training was introduced in 1990 to ensure that all riders taking to the roads unsupervised on L-plates would have had some basic training. The intention was that riders would then go on to take the tests to obtain a full licence, and they were given 2 years to do so. Unfortunately, a lot of riders choose not to continue their learning and so their CBT certificates expired after the 2 years were up. In which case, they need to re-take a course of Compulsory Basic Training. There is no short-cut for CBT renewals, the full course has to be retaken.