8 years on the location using low/hi, and little to no wear on the concrete or equipment. I am thinking we must wash everything off well enough with rinse cycles to keep from getting damage. This wash is in farm country so it gets a lot of dirty vehicles with road film too. Really have it dialed in, and haven't had a wash quality complaint in a long time. As far as dwell, this time of year we barely pause between presoaks. In the spring we will dwell for 10 seconds at most. I have found, for this wash, it is more important to apply chemicals on a dry car, no galtun guns or rocker spray, than it is to dwell.