When I was there 5 years back (3000+ hrs there) most Captains would alternate legs....really green FO's might just do empty legs till they had better skills since some new hire FO's do struggle with the transition to the pc-12.
Know there was a bit of a management shakeup after I left....company had been a great place to work when based in MHT, but the move to PSM changed many things...many would have left sooner if more places had been hiring in that timeframe.
Many summer days in the Northeast can be a grind....doing as many as 10+ legs in a 14 hr day, but the seasons change, things shift to longer flights and 2-4 legs were the winter norm does mix it up... actually helps to prevent pilots from getting sick of it...keeps it fresh.