Well considering that I use 2-3 pumps per shave and I always end up with enough lather to shave myself and a boxcar full of hobos, I would think that a three pass shave plus touch ups could be done with one pump of KMF, which I would think puts an 11oz bottle in the 8-12 month range.
If you first load your brush with a shave soap then use a bit of KMF to create a "superlather" I would think a 11 oz bottle could go more than a year.