I used to have that level of motivation for work, i dont think ive made a real effort since i became full about 3 years in. I couldnt be arsed 
I've only ever done it once, but the work i gained from it was more than worth while, if they didn't phone i used to go around with a clip board and ask when they would like booked in for there free clean. If you can get the house building company on board it makes it look alot more professional, as they read the welcome back and will see the leaflet in it, so your already something they have seen and puts them more at ease i think.
Sure you won't get every house you do, you get more than you dont though. It's alot of people's first homes, they are still in the mind set of keeping the appearance all nice etc. It's the best possible time to get people on board to get it cleaned regularly.