I think I did 3 batches of pre-hopped cans and then 4 batches of extract w/ steeping grains before my first partial mash.
I still PM (and don't see that changing anytime soon - brewing outdoors is really not an option for me from about March to October, and my kitchen stove can't boil more than about 4 gallons), but am steadily increasing the grain to extract ratio I am using. I started out with doing the mash in the kettle, then I used an unconverted 2-gallon rubbermaid cooler, and I just converted a 5-gallon rubbermaid cooler into a mash tun with a stainless steel braid and ball valve.