Not to cause a stink or such, but these engines were designed and built by folks that are waaaaaay more knowledgeable than I, so if the recommend 7500 miles (5000 sever conditions in my case as I pull a heafty trailer), then bottom line .... I'm going to follow their recommendations. If you feel you need an OA, go for it. By the time you get your pre-filter, synthetic oil, super duper mico fine oil filters, etc, etc so you can go for extended changes, you could have been doing it every 5000 miles with dino oil and not spend any more. If your still paranoid, do an OA every other oil change. As to seeing commericals about "hey, we used XXXX oil, driained the crankcase and ran it for an additional 1000 miles". Uh huh, and my neighbors bull produces 25 gallons of milk a day and can jump the moon in a single bound, blindfolded! I have yet to see definate proof that say starting at day 1, you take 2 identical engines (#1 one only serviced with syntheic and all associated stuff, OA, extended oil change intervals - and #2 maintained according to mfg recommendations), in 2 identical vehicles,ran the identical way with identical load and operating conditions, and at the end of say 100,000 miles, torn down and the syntheic engine being in better shape than the dino engine.
Just my two cents, but I have better things do do with my hard earned money.
Larry