Went to the "wash as long as you want; up to 30 minutes" in 2000. I was $4 then. Raised to $5 around 2005. Then raised to $6 in 2015 (wish I had gone to $7). At 5 locations, volumes are above the average reflected in the magazine surveys. As a percentage of sales my chemicals and water/sewer run a tad higher, but not significant.
My goal was to keep folks from racing around their vehicle, doing a half a$$ job. Before, I was $2 for 4 minutes, like most operators. In my opinion, it is not a good customer experience racing the timer then leaving with a partially done car. Once my customers got over the shock of the start up price, it has been a good fit for my locations. Folks will wash even when rain is foretasted because they perceive it as such a good deal. They wash in the rain in some cases. I feel it has built a really loyal customer base.
I have double traffic loops in the floors to keep more than one vehicle from washing on the same time. If a second car pulls up; bay shuts off. When car pulls out, bay resets. If 2 cars are in to begin with;
coin accepter is disabled.
I do average time tests occasionally. The last time I did that, the average washer used 15 minutes. In the winter it was 22 minutes.