With around 45 very experienced captains due to be re-fleeted over the next 10 months I wouldn't hold your breath on the DEC score. As for the cadets, they usually stop being cadets around 15 months after joining, and are in the command experience bracket at around the 4.5 - 5 year point. As they usually only form around a third of any recruitment drive, there is no shortage of experienced First Officers to draw on, even when TTC (Time to Command) falls to the 5 year level or below.