We switched from 18212 to 18209 in 2008, after about 80 passes on the 18212's. Just ran 2 seasons [214 passes] on the second set of 18209's, and 60's were the best & most consistent we've seen right to the end of last season...once we learned how to do a "proper" burnout! I.E. - only clean them till they start to haze, not try to set them on fire!!
