Mikey & Jim Pemberton made some good points above / MAINTENANCE is a win-win for you and your customer... It's easier for you to take care of a well-maintained carpet. It builds you up a route of maintenance contracts that you can bank on servicing month after month. It enables the customer to expect clean carpet year-round. It helps the building owner to project a budget for carpet care. And it extends the life of their carpet investment.
This is based on commercial carpet care, but could be morphed into residential as well. Think about it... People hire monthly lawn care services, pest control services, they have a service contract for their HVAC system, etc... So why not carpet care too?