You are thinking about it in terms of "how do I get paid when I am only showing up every two weeks?" Realign your thinking. On a $125/mo lawn, I don't want them to look at it as they are getting four cuts (or five on occasion) in the summer for that amount and getting only one or two during the winter for that amount. I want them to understand they are paying $1500 a year and it's simply divided into 12 equal monthly payments.
Going every other week varies for me. Sometimes it will be as early as Nov 1. Other years as late as Dec 1. Just depends on what the lawn and hedges are doing. I have gone back to every week as early as late-March and as late as the second week in May. All depends on the weather. With most of my customers I pretty much explain to them the way it's going to work, and all but one in the past few years has understood and been happy with the arrangement. I am not guaranteeing a number of visits, but I do use an estimated number of visit to arrive at my monthly price. Some will ask specifically how often you will be there in the winter. Most of mine don't.