I've got a Tsubaki which was recommended by Italia in Lincoln. Used it for half this year doing several track days and it has hardly needed any adjustment. Amazing really. (probably leaving myself open to sarky remarks about my riding now of course!)
Mood: So its raining, your problem with that is ??
Looks like the sigma then....
Maybe its my "Over-generous" use of the clutch to hook it up that has killed the last one... Or maybe 14,000 miles in a year has not helped either,...nah...I'm just heavy handed..hehe.
Henry, I would suggest that a smooth riding style is the reason your chain has not needed adjusting...