Sp3 goes on for min 60 hits up to 3 minutes. I even pause for a second or two after every combo to see if he’ll trigger it.i just kept going for 3 minutes. Tried to see how long he’d stay sp3 for. 
Also does it with sinister and destroyer,not just herc.
  everylastint sp3’s
 https://youtu.be/Y427kRzTHgM
https://youtu.be/Y427kRzTHgM