I'm wondering about running the new Endurance filters at around $12.95 each for two OCIs instead of the single OCI I have done for years with both old and new Ultras. I cut up a bunch of old filters yesterday and both old and new Ultras look fine after 5-6,000 miles using 5W-30 synthetic. I've been going on a time-based oil change regiment for all vehicles for the past few years. Change both oil and filter every six months (around May 1 and November 1). I like to dump the winter oil in the spring no matter what the mileage because it has endured numerous cold starts over the winter. The most used vehicle might run 5-6,000 miles during that period, so potentially the Endurance would be on there for 10-12,000 max. That's still less than half the claimed rating on these things. I'd plan on changing it around May 1 each year. All vehicles are well beyond any warranty worries, don't burn oil, and otherwise mechanically sound.