Dwarf Evergreens Get Big!
There is really no such thing as a dwarf conifer. All grow throughout their lives. So the tiny little conifer that looks so good in your rock garden and which the label promises will measure 3 feet (1 m) high by 5 feet (1.5 m) in diameter may be one day as tall as your house and nearly as wide! In your calculations for spacing “dwarf conifers”, you can easily double the height and diameter listed on the label. This will give you a more realistic estimate of its size in 10 to 15 years. And seriously consider removing them after 15 to 20 years, because at this point, the term “dwarf conifer” really no longer applies!
I’m not trying to discredit dwarf conifers. I find them very useful in home landscaping… and 20 years of service is excellent, but to truly profit from them, you have to know how to properly space them and you also need to know when it’s time to replace them.