All my customers are new so therefore "first cleans" I make sure I take extra care and even dry all the sills and frames ect, If they are in when I do them I escort them round for a "check" if they are not in I arrange to phone them that evening to make sure they are happy - so far everyone has booked regular cleans and Ive not lost a customer. However, I know this won't carry on as you always get the odd one. Next week I'm going into the second clean with some and I still dont feel quite confident to leave them wet, but I realise I have to, so for the second clean I intend to leave them and return the same day once dry to re-check my work, if its ok I will have the confidence not to return the third clean, if not I'll know where the problems are.