Some thoughts on Wildcat1's post:
Moving up to the 99 is dependent on what base you're at, your willingness to take an outstation when it becomes available, seniority, and luck. Some bases go very senior, and there's very little movement in the turbine a/c. And then, sometimes there will be several people departing, and there's a mad scramble to fill those slots. To be fair, I would emphasize that upgrading in a couple months is a rare exception- 8 to 12 months would be more likely, unless you're at a junior base or take an outstation.
Turbine upgrades have been all over the map recently- I upgraded after about 8 months, because several people declined to take the upgrade. Since then, we've had the next candidate pushed back several times. At the same time, we lost several outstation pilots, and low-seniority pilots from other bases who were willing to move have upgraded to the 99. Several months ago, we were hiring direct to the 99 to fill empty slots, and then suddenly several pilots who thought they had been hired to the 99 were informed that AMF needed Chieftain pilots at a different base- and that's where they ended up.
Having said that, I can say that at my base, I foresee a constant need for Chieftain pilots and possibly a couple 99 pilots within the next 6 months-1 year. I do expect one or more outstation pilots declining to stay at their outstations after their six months are up, which means openings that will most likely go to off-base pilots who upgrade to the 99 to take these outstations.
In summary, to get a quick upgrade, the best route is to be based in BUR as 'system reserve' and be willing to go out to the boonies as soon as an outstation opens.