as much as i love as group IV oil, which M1 and the high line Amsoil are, i wouldnt necessarily shoot for the 5-6k intervals.
it sounds like you make a lot of short trips which are notoriously hard on engine and oil due to moisture contamination. Since these short trips may not be generating enough heat to "burn off" the moisture that forms in the oil during the combustion process, it may be forming acids. these acids will attack soft bearing surfaces. M1, like any other oil, can become contaminated, and once the levels of harmful acids have over come the additive package, bearing surfaces are at risk.
also, if the engine is usually operating in warm up mode, one can expect greater than usual amounts of fuel comtamination in the oil.
i would suggest using Auto-RX to clean out the engine, then switch to a good quality dino, like penz 10w-30 which is rumored to have some moly in it, and change it several times at 2000 mile intervals. Then after the second or third 2k interval with Penz, do a UOA to see how things are going.
I use M1 and extended drains, because my car sees about 200 miles a day, with about 70% being interstate. The remaining 30% is city, but the engine seldom is run at anythign but op temp.
I also flush the trans once a year, and change the filter once a year combined with three "pan drops" which changes about 40% of the atf each time. fluid is cheap insurance coupled with my B&M trans cooler.