5 hours is a long time. I used to go to the groomer who would also tell me 3 hours or more. I refused to go there. It seems too long. In my opinion, you make an appointment for a reason. It seems the bigger grooming place the more time you wait.
It must be because they take numerous dogs at the same time to groom.
I found a smaller place where my Maxi loves to go. I bring him in and in 45 min to an hour he is done, and I pay half price of what the other place charged me.