Agreed.
I like to stay with a given oil for at least a few OCIs, since I feel that this maximizes additive package effectiveness, whether I'm right or not.
If an oil is offered at a deal, I'll check the UOA forum for it, and if the UOAs look good for my intended use, I'll load up.
For example, Meijer clearanced out their four quart jugs over the summer, Valvoline offered their "engine guarantee" rebate, and many of the Synpower jugs had $1.00 off coupons attached to them.
Synpower has shown really good results on 5-6K UOAs, so I jumped.
I bought seven gallons of Synpower, enough for the next five OCIs on the Forester, now on the very similar VR1, with three quarts left for whatever at a dirt cheap price after coupon and MIRs.
Prior to this, I had done maybe two OCIs on anything using Valvoline oils, but the price was right and the oil seems to hold up well for the drain intervals I intend to use.
I've used PP and M1 when similar deals were offered.
Buy what works when it's cheap, but buy enough to use for at least a few OCIs.
That's about as far as I go with brand loyalty.
I'm more loyal to my wallet.