I am lucky to use the same oil brand more than twice in a row.
I am the same as above, for the past 10 years or so, I have used whatever is on sale/rebate/clearance. Sometimes I get 2-3 changes worth, sometimes not. Sometimes I have a bunch of odd quarts and make a frankenbrew out of it (6 different brands once).
Before I came here, I did use Valvoline exclusively, but even that was always bought on sale and with rebates. I just like Valvoline, not for any rumored benefit of using the same oil for the life of the vehicle.
My Scion has had 5 changes of TGMO ("free" changes with vehicle purchase), Pennzoil Platinum x2 (or 3?), Auto Zone Syn, and now Quaker State Syn (and next change will be the same).
My truck has had 2 changes of Havoline HM, 1 or 2 with some Valvoline Next-Gen, 1 with Castrol GTX syn blend, 1 with a frankenbrew of Pennzoil Platinum/Next-Gen (50/50), another frankenbrew of 6 different brands of oils (conventional, blend, and syn) and currently has Castrol HM. Who knows what was used in my truck for the first 120,000 miles.
Thing is, my truck goes through a qt every 1500 miles, so I add whatever for that, from "used" oil from my wifes car to Mobil 1 (sad when I use top tier oil for "top off" oil, but when you get the stuff for qt, why not).