The way I see it is that it pays to be flexible these days.
I allow my customers to decide what frequency they want. I have some weekly shops, plus residentials from 2 weekly to 3 monthly, as well as a good number who call me as and when they want.
It all works out well for me as I have plenty of work to keep me going constantly, therefore if one of my customers asked me to leave for a couple of months, it would make no difference to me as there are always others to do.
John