Have had dizziness & nausea on & off for 10 years. i was told by ent re-balancing of crystals was required, will that treatment be effective now?

Probable: Humans have tiny calcium stones within our auditory system inside semi-circular canals that are used to control our balance, sometimes these stones come out of place and cause dizzyness ( vertigo), puting them back into place by using a certain maneuver called epley's maneuver can solve this problem.

Possibly: If you are truly having benign paroxysmal positional vertigo, repositioning maneuvers typically are successful. Some patients are prone to recurrences and need to be seen for this procedure. I would recommend seeing your ENT again.