I haven't noticed much stretch on my 18" tracks after putting on about 40 hours the last couple of months, not enough to take out a grouser anyway. What I have had happen though, is I have lost a few bolts on the outside edge of the tracks,I believe that the extreme flexing of the outside edge might be loosening the lock washers. I retorqued all the bolts,and will let you know if this is an isolated case, or if they are in fact getting loose.I picked up 1 lb. of bolts, washers,and nuts just like tim uses for $1.89, and keep them under the seat. No problems on the inside bolts.