If you need to clean your carpets once a month you need to change your carpet cleaner! If you set about your carpets with a shyte machine and tons of detergent to make up for the poor machinery, you'll just ruin the carpets and frustrate yourself! (using cowboy "professionals" has exactly the same effect too.)
Leaving loads of detergent behind will make more dirt stick to the carpets, you'll get into a vicious circle of more cleaning, putting more detergent in the tank, leaving more behind each time, carpets get dirtier......
I'd suggest you find a really good local carpet cleaner and maybe make some sort of "arrangement" to help out with the pricing side of things, if you're trying to save the pennies.
Even the most extreme situations customers throw at me (kids, pets etc) I'll only be there every 6 months or so.
Or are you or the mrs a clean freak?

one speck of dust and the whole lot has to be scrubbed! I have some customers like that, keep the cash flow going nicely
