Happened to put my hand on the inlet pipe in the DSH loop to the buffer tank today---noticeably warm!  So the DSH (which had the valves mistakenly closed most of the summer) is definitely working.

Prior to all this, my 50-gal propane tank would basically poop out after filling the whirlpool tub once.  You could basically just run the hot water straight into it, and by the time it was full the tub temp was only bath-hot, since by then the water from the tap was lukewarm.

Last weekend I ended up needing a nice hot therapeutic bath.  Absolutely needed to include cold water in the mix to get the right temp.  An hour or so later, my wife had the same idea, and refilled the tub.  Again, plenty of hot water.

Big, big improvement.

To refresh the collective memory, the new system is an 80-gal electric fed by a 40-gal buffer tank connected to the DSH.

Glad it seems to be working for you