The problem
Referrals are lovely right up until the month they stop.
Word of mouth built your business and there is nothing wrong with it. But it is not a tap you control. When the diary looks thin in February there is no lever to pull, so you buy ads, pay for a click, and if that person is not ready this month they are gone. Then you pay again for the same person in the spring.
Meanwhile the two hundred people you have already installed for, who trust you completely, hear from you once a year when an automated service reminder goes out.