If they have givern you a phone number at the time of the quote i would say they are pretty genuine.
i always record these into a book then call back between 5 and 10 days later to see if they want to go ahead
it always helps if you know why they did not go ahead on the day ie.. speaking to hubby/wife etc... this gives you a great 'in' with the phone call.
we don't offer any further discounts just because they dither on whether they want a windy or not. - that's done on the day and only in rare occasions if i know i was heavy on price
Darran