Well colour me purple I can not work this out.
week 1, your flat out
week 2, your flat out
week 3, your flat out
week 4, your flat out
money = flat out x 4
So, you move em all to 6 weekly...
money = flat out x 5.2 (thats if you raise a 5.00 to 6.50)
only solution is to raise them by 50% each or more. Excuse me Mr Customer, I am going to be doing your windows less often but still want the same per annum. I can not see that working.
Now here is something I have just come up with which might make you think about how you want to solve this problem.
Asda, chances are your local shop keeper would love to own Asda. However it is an absolute monster he can not compete with, his prices are probably higher and Asda is known for its "stack em high sell em cheap". Every Tom, Dick and Harry thinks that is how Asda makes its money. However that is not strictly true. Your local shop keeper is on to a good thing see? He could, if he wanted, go and work for Asda. He chooses not to because they could not afford him. His hourly rate is way way above what Asda pays. That is really how Asda makes its money, paying low and selling a lot (I am sure they pay more than some but they are not on 20 quid per hour)
Likewise for you. You could style your business on Asda if you wish to pay your staff a fairly low wage. However I am going to fire a wild guess that you are the only employee of the company. That means running an Asda style business on your own would mean you reduced your wage bill ie your income.
This is not at all what your after. Ask yourself what your local shop keeper would do if he was the only wage bill and he was over run with customers. Would he think "I know, if I offer my customers a better deal for buying in bulk that will solve my problem"? No, it is far more likely that he would either take on some staff or hike his prices a bit. If I was him I would hike the prices and if it still carried on growing then I would take on extra staff.
As a window cleaner you might not wish to take on extra staff, but you can certainly hike your prices to reduce your work load or at least make it more worth while rushing about.