While I agree that certain instructors are a better bet for quality training, I disagree with only looking for one that has been diving/teaching cave diving forever....
Remember that there was no such thing as a cave cert when these guys started teaching cave...they made it up as they went along...just like every other niche in diving.
Look at wreck diving: 20 years ago you would be called suicidal to run a line inside a wreck.
If you know where to get good y valves(the ones with actual knobs), please post a current link. I haven't seen one on the market in ages.