To be honest jay saying you will be there between 8 and 12 is a big window of 4 hours for someone to have to
hang around for you to turnup, when I'm very busy my max window is an hour which most people accept,
but 4 hours is half a working day for most people.
I always try to be as accommodating as I reasonably can, and I can usually work around customers' requirements. Some however, seem not to be quite so flexible.
I have a run of shop fronts, and one wanted theirs cleaned as soon as they opened. It had a metal cage protecting the shop front which had to be removed first (not by me).
I turned up ten minutes after opening to find they were already in the process of being cleaned by a young lad working in the shop. This had happened before when a friend of mine had this shop, which was one of a number that I took over when he emigrated recently.
I walked in, said to the lady behind the counter "Hi, just letting you know that I am here, so I didn't let you down, but I can see your man has got there before me. I'm just leaving that with you." I then said (smiling) to the young lad "You're doing a grand job and keep up the good work!" and walked out.
John