I set mine at 24" and basically start planting right away.  It will take 30 min to get down to 3".  The funny thing that I found is my actual accuracy does not improve with time. 

What I mean is I run a 16 row Kinze Planter and the outside carrying wheel comes back in its own track.  It works just as good on 24" convergence as it does 2"  I don't know how or why but it does work.