Timing chain wear and stretch is determined by several things like quality, presoaking as well as the use including valve spring pressure and maximum RPM ran on each run cycle I've used Cloyes mostly and the better True Roller seemed to last quite a while in my bracket motors shifting at 7000 RPM with flat tappet cams and valve spring pressures under 350 Lbs. My old Duster motor with a solid roller cam and 680 lbs spring pressures had the best Cloyes unit offered at that time, billet gears and so on and it failed , broke, after 2000 to 4000 street miles and hundreds of runs shifting it at or above 7000 RPM in each gear that chain never showed any stretching at all when I had the motor apart twice