It varies greatly depending on the unit, the ability of the trainee, the consistency of the training, quality of training, instructors etc...
As an example, from finishing my TVC, it took me 16 months to validate on the North bank at TC. The reason it ook so long is that I was 3rd in the queue for live training for a while and didn't get consistent training until about 8 months before validation. Once I began to get consistent training things began to move quicker.
Also, halfway through training the hours requirement for each level was increased, upping the expected validation time by 100 hours. I think it took me roughly 450 hours of live training to validate, 300 of which was consistent.