There are 3 principle for making more money in business,
1) make customer spend more money by increasing prices,
2)make customers spend money more often by increasing the frequency of their cleaning
3) make customer buy more products or services
Your point ties into number 2, if customers only clean their carpets when they look dirty we cannot increase the frequency of when they call us, but if we can educate them to have their carpets cleaned before they look like they need cleaning then they will use our services more often