It may sound rather obvious but the easiest way to keep a surface free of moss growth is to stop it from growing. Don't spend time killing and clearing moss but stop it growing in the first place.
Unfortunately, most of us do like to put things off. This is especially true with jobs that aren't particularly exciting and sweeping or scraping moss certainly doesn't strike most people as an exciting way to spend their time. So, what happens? Areas are left and over time moss spores take up residency and grow, albeit slowly, into lumps of moss, lichen or just greening. We may feel that it has grown overnight but really we have given the spores all the time, space and food that they need to grow. However, it needn't be like this.
You will find that a little forward planning will save you a lot of time so plan to spray an area every 6-24 months. Areas that retain moisture, such as tarmac or shaded areas, will require more frequent applications so maybe every 6-12 months but areas that receive more sunlight may not need an application more than once every 12-24 months.