There is so many things that affect drying times, one of the main things is the climate and humidity at the time of the clean, the customer can affect the drying times by making sure of good ventilation, keep windows open a little etc once you have gone home.
How many times have you gone into a job, the radiators are on full and all the windows are closed. And they thinkl they are helping you

Make sure your vac on your machine is working to its full potential, make sure all the hoses are in tact(No splits or loose cuffs) the seal on the dirty water tank is in good condition if your a porty user.
And finally only put down the minimum of water you need to do the job and plenty of dry passes.
You can install airmovers and dryers if you wish, to be honest i do use them on suites but hardly ever on carpets.
Mark