I'm also using a Bully clutch, Stage 1 (Kevlar & organic combo) in my OBXT with a resurfaced (Bully did it) dual-mass flywheel. It's a year old, 15,000km and it now slips in 5th gear. I spoke to Bully about it and they suggested four things that would make it slip:
1) contamination, any small bit of oil from the enigne main seal or grease from the shaft
2) the Kevlar will glaze if slipped a lot and the glazing needs to be worn off through some hard starts
3) the pressure plate is not exerting enough pressure on the disk. They can adjust the pressure after bench testing it if it's not enough.
4) the disk is worn, the flywheel is worn, the pressure plate is worn
I'm hoping mine will hold till spring as I don't have a heated garage to work in. I'll take it in to them and have them test it. I also have my old clutch parts which they said they can rebuild which will reduce my down time and cost. So far customer service has been good and for me, they're only 15 minutes from home.