18 months seems quite quick for that era. I would say most instructors and turboprop pilots were stuck for nearly the best part of 5 years before moving on (if at all) in that post 9/11 era between 2000 to 2014 (slight recruitment peak around 2007).
However what everyone is overlooking is the return of the pay to fly schemes, Eagle-jet adverts which have disappeared during the recruitment boom have now reappeared with a resurgence on latestpilotjobs. While I disagree with pay to fly, the fact remains the low hour qualifiers which can afford to do it probably will. In the last down turn many low costs ran pay to fly schemes (Easyjet via Johnathan Kurds company, Wizzair via Storm Aviation), which invariably halted the progress of experienced turbo-prop pilots.