I will do, and its not a matter of turning down test drives, its whether youve offered it or not. Most customers are appointed, so you can ask some questions before you even get them on site. I had one last week, he was booked in, had a quick look around and then asked for the test drive. I asked if he was happy with the condition of it and the price. He said he expected a discount. All my prices are fixed, I told him so, he was with his other half so they had a proper look round it then and a chat between themselves for 20 minutes. Then asked for a drive again because they thought it was ok for the money. Drive done, they paid for it and drove away.
You have to control them. Its your Insurance risk, your fuel, your re clean cost. Make sure all the ducks are in a row before the test drive, and it makes life easier. Some will always slip through. And be blunt about the purpose of the test drive; its not for you to find out how a focus (or whatever) drives, that was the manufacturers job x number of years ago. The purpose of this drive is for you to satisfy yourself theres no noises or problems. Thats my take on it anyway.