Your previous experience means nothing once you have the job. Cadet, GA, RAAF... doesn't enter into the equation.
Your progression depends on expansion of the airline and to a small extent, retirements at the top. It can change in the space of a week.
Current joining SO's would have about three years as an SO on average. During a downturn that can lengthen dramatically, or shorten to around 18 months in an upswing. Just enjoy the job.