About a year and a half ago they ran one or two of the PS planes on the LAX-BOS route for 6 or 8 weeks. They just sold the seats as F and didn't sell the flights as PS. It's not clear if it was dipping a toe to see if there was a market for PS on that route, or if it was just part of moving aircraft around to cover routes due to seasonal schedule changes and maintenance. IIRC there was a thread about it, or a discussion of it in the main PS thread.

For me, it already takes long enough to get LAX-BOS, between getting to LAX and getting an hour west of BOS when I get there, so I'll take a non-stop on a 739 over a change in SFO with the extra time and chance of weather delays.