My final trip was just under a year ago (I decided to keep a tonne of miles to convert to Avios as they are valuable for my European travel under Reward Saver redemptions).
Was a sneaky one-way!
BFS-EWR-PHX (X) PHX-ORD-EWR all in J (UA)
God knows how many of these trips I was able to book without them noticing I was passing through the Airport I was eventually going back to... :/