I used to do shortened oci's too for a long time (18 BMWs), back in the good old days of dino lubes and bias ply tires, and before BMWNA when the Monroney sticker on BMWs said Hoffman Motors. But man's understanding of how oil performs inside an internal combustion engine has improved significantly since then. Just remember that when you change the oil you are dumping lube that has reached an All-Pro level of performance with one that is a rank rookie that will take several thousand miles before it can figure out which way is up, particularly in combating wear - http://papers.sae.org/2007-01-4133/
. But, don't worry - - BMW motors are tough - - they can take the abuse of too frequent oil changes! Me, I believe in keeping the All-Pro in the lineup as long as possible.
Someone said that these arguments (shortened oci's vs oem oci's) are a silly debate. To an extent I agree. The Ford research mentioned in the SAE paper shows maybe a technical phenomenon, but as a practical matter, is it possible that shortening the oem oci can significantly shorten engine life? I seriously doubt it. But on the other side of the coin, I've yet to see any credible research (SAE, ASME, STLE) that shows shorter oci's (shorter than what the oem recommends) prolongs engine life.
What I object to in these discussions is the idea, either implied or explicit, that anyone who adheres to the oem recommended oci is some kind of pathetic, ignorant cretan who will take his BMW to an early grave. Bulls*#&t. As my old boss used to say, "Show me the data."