So your shadow Pokemon's gone into hyper mode. What do you usually do? Do you call it straight away to help get it closer to purification, or do you keep it in hyper mode for a while for extra critical hits?
For me, I may keep it in hyper mode if I'm facing a particularly difficult opponent, or if my Pokemon can't learn any more moves by opening its heart further. It has, however, frustrated me a few times after a battle when I can't heal it up, so I would usually try and call it before the end of the battle if I have a chance.