I book 2-3 US-Asia Biz class tickets a year for myself. I have a return for this month, but I'll credit it to CO. Add in my domestic trips, plus Skyteam partners, and it's about 20k for my family per year.

Otherwise, I'm not spending any money on DL or NW unless I can absolutely help it. I have enough miles left to fly for another year or so for free, which is strangely convenient, since that's how long my Plat status will last.