Hi Les
10 - 15 minutes every 30 minutes or so? Doesn't leave much time for the poor floor singer who's been sat there for for a couple of hours!
Seriously I much prefer that if an artist wants to come into a SAR then they get their turn the same as everyone else perfect example was Si Khan the other evening. I usually manage to avoid the type with pre-booked guests spots, to be honest that's not why I go to SARs it's to listen to everyone and to join in myself.