I also price per frame and don't worry in the slightest how long it takes to do the job.
For instance I did a first clean inside and out on a local salon today. It took me over two hours to get it to a standard that I was satisfied with, and the hourly rate would make the so called big boys on here laugh (or cry). However, the owner was delighted with my efforts and the job is booked in now as a regular, and will take a fraction of the time to clean in future.
I couldn't have cared less how long it took because I believe that taking extra time on a first clean equates to investing in that customer, and that investment pays for itself over and over through regular custom and recommendations.
Barry, take no notice of those who put you down. As long as your customer is happy with you, and you are happy with the job and what you made from it, that is all that matters.
John