There are no immediate plans on the line to buy diesels. Passenger locos are 6911 and 6631 between Chabuga and Daban, and 2645 between Daban and Haoloku. Most locos run their service between the turning points, where they immediately are taken over by a new crew and turn round to the next train. So the number of engines standing at each depot is normally small. The Daban engines all are manned with three crews.
Most people are quite young.
Seldom above 30. This schedule is maintained if there is a lot to do, and until a washout. If there is less to do the standing times at Haoloku or Daban get longer. I saw turnaround times of about 10 hours on one hand, but 24 hours if there were less trains to run. The new crew takes over the locomotive at the depot, checks the motion, puts oil on, and gets the slag out.