Maintenance is all about repetition. You'll be repeating the same tasks week-to-week all season-long. If you underestimate on an install job, you'll learn quickly and adjust your pricing for the next job of a similar type that comes down the pipe. On maintenance however, if you underestimate you'll pay for it all year long.
I could sit here and type out an essay on how to estimate for maintenance, but instead I'll recommend that you pick up a book this winter and give it a read. The book is called, "How to start a Home Based Landscaping Business" and it's written by Owen E. Dell. Order it from
www.chapters.ca if you can't find it in store.
It's all about the business side of landscaping (maintenance and installation) and assumes you already know to plant sod 'green side up'.
As far as quick formulas for maintenance, no I don't really follow any. The services may be the same, but the properties are all different. Sure, there are rule of thumb formulas such as 1yd of mulch will cover 100sq.ft. at a 3" depth, but there's a big difference in how long it will take to spread that mulch in an easily accessible front yard bed, compared to one way in the backyard down a steep slope through a small gate.