I have one maintenance crew and haven't mowed grass in years. It all really depends on how much overhead you can afford to have (i.e. Owner salary, non-billable). Keep in mind though I am over 85% snow, and pretty much my entire overhead is paid for by snow.
And whenever an install job comes our way, I have to be onsite leading the project as I don't have anyone who is high skilled enough to take a hardscape job from start to finish successfully. But I don't focus on that, so the workload is not there to hire someone to take it on.