If you check you conversion efficiency, 97-98% conversion is about the upper limit. I suppose 100% conversion efficiency is theoretically possible, but I never get there, nor does anyone else I have spoken with who actually tracks such things.
I stir about 3 times during an average mash, and more if I am not getting my conversion efficiency to about 96-97%. I find you can lose a large amount of conversion efficiency and therefore gravity points by allowing the mash to sit statically. It could be system specific, but I know how my brewery works. Before I paid attention to my efficiencies I didn't know about that and didn't stir as much.
How do you track conversion efficiency? PM me if you dont want to highjack the thread.
I use a RIMS system and you will need to stir during dough in. I stir once @ dough in, returning the mash through a simple CPVC manifold atop the grain bed and Batch sparging (with a mashout). I consistently get 90%+ eff. My efficiency is calculated by PROMASH.