Quite honestly you don't have to except it, or put up with it in this day and age, a lot of shops no longer accept chq payments ! (For example)
There are several options you can take.
Simply do a letter to those customers who fail to pay on time letting them know it no longer viable to collect in an evening, we provide free alternative ways to pay such as bacs and go cardless or they at there expense can post payment within 5 working days.
Or you would be willing to collect however you would have to increase the window clean by £2.00 to cover the costs of the extra visit.
We do a customers newsletter and mentioned it in there first, then tackled any stubborn customers on an individual basis as above, be apologetic, play the poor old window cleaner card, cost of petrol blah blah....
I haven't collected in over 2 years now (bliss) and I don't recall losing anyone, and now it's never questioned by new customers
Darran