When does it become more important for the team to work on player development as opposed to a push for the playoffs?

In my opinion, this season has been a great success to date.  I thought the team would have a chance at the playoffs, but I also thought 45 wins would just about do it.  But we are getting to the stretch run, and being 6.5 games out of a playoff spot with 17 to go, its looking like the playoffs are more and more of a stretch.  I'm curious when you all think the team crosses the threshold and begins to look at the bench players a bit more.  Or, is the push for the playoffs the learning and developing experience the players need?  When should we expect to see McRoberts, Von Wafer and Sergio more?