Richy
I would agree. If you ask people for their preferred day of the week they will generally say Friday and on our domestic rounds it is the first/easiest day to fill.
But its not impossible to "educate" your clients and also to use a little bit of psychology too
Here's what I do
I ask people if they they have a preferred day of the week
If they are not fussy I will say "I think we have a vacant slot on a Tue/Wed/Thu" or wherever you are trying to plug. Keep your premium slots for those that really want them.
If people want 2 visits per week I try and encourage them to go Tues & Thursday
You can "sell" Monday by saying that "its just after the weekend, they don't have to worry over the weekend" because it will all be sorted Monday.
The other thing to "sell" is the regularity - if its going to be done once a week every week THEN IT DOESNT really matter what day of the week it is.
Another thing you can do is have a waiting list for Premium Days because its a simple fact of life that customers come and go and for a variety of reasons- we can put you on Tues for now but when a vacancy comes up for ,,,,, we can swop you.
Hope this helps - its a bit more practical than theory for a business plan
Mick