Wannabe24
Having been there myself not too long ago, I don't know any recent FO's who have remained on the Dash for much over 12 months without at least being offered a RHS on the 145 or RJ (possibly at another base). I flew the dash for 10 months before going on to the Embraer.
Company policy was to 'type freeze' FO's for 2 years, but due to the low salary, most of them would have disappeared once they had 500 hrs multi crew time!! Another issue was the fact that some new joiners were going straight onto the jets, and starting on around £12,000 pa more than the established Dash FO's! (which didn't go down too well)!
Not sure what the latest policy is but wouldn't expect it to be much different.
W-S.