I've thought about doubling the filter change time. I think the 3.6 is easy on oil. I do it on my JK 3.8 with Ultra filters and they come out looking great after 12k. But, with 12 clearance Walmart M1 filters on deck, I just can't bring myself to go 16k on them.
If I were wealthy, I'd run an Ultra or M1 and stretch the M1 AP out to 20k and see what the UOA showed. But I have a lifetime warranty, so OLM decides it. I ran 7500 on the AP/Ultra combo and the oil came out in great shape with no sign of falling off. I think it could have gone much further. And, btw, I don't baby this engine. I run it hard. That 7500 mile run included a lot of rock crawling and also twisty road driving going through the gears and seeing a lot of high RPM.
I really love this engine, especially mated to the 6 speed manual in the JL. It is just a sweet combo.