I took my Sebring to a local brand name lube shop, within a week I had major transmission problems. Not suprising on a 96 Sebring. Their fault? Only in my fantasies, but I never went back. Later I heard of two other vehicles for which they bought new motors, after various oil change related errors caused problems.
Anyway, advice that costs someone $120/yr instead of $60 while providing a plausable benefit isn't going to draw attention, but it will double your annual profits. Advising some one to skimp beyond mfgrs. recommendations, that will get you in deep water quick.
PS. I've owned 3 new vehicles, each clocked over 100k, I wish I could say I changed the oil every 7500 miles, but most often it was more than that by 500-1000.