So since Dec. 24th, I did 5 runs, between 30 and 50+ minutes (that one was interspersed with walking over a total of 1-2 hours).

I massaged and stretched a lot and I stuck with my new year's resolution of earning every single run with a session of core work and stretching - either immediately or separately.
So far I've run "pain free".

Today in the PT session she advised to keep to the ~30-40 mins until the next appt. in 2 weeks. Ok, I'll be good. My body has been teaching me lessons:
As mentioned elsewhere I made up training time with too much swimming (was bored!!) - and ended up hurting my shoulders. So this means a week off, reduced yardage, no more paddles or attempts at fly, and more stretching.

Don't know yet what to do about the back which is still very tight. I'm a glutton for massages by DBF but it's only temporary relief.