Reah,
That was exactly the same as my experience, which is why I took a keen interest in your post; to see how it worked out for you.
I think you have to be in the position where you're earning a good bit more than your expediture and be able to take a 3 week, extremely restricted cash flow. One or two weeks to get the cheques in and a week for them to clear.
I'm getting towards that position; and may do one collection a week - on a Friday and leave a note saying 'Couldn't catch you in - post a cheque to blah blah, etc'. Rather than my present Friday evening, Saturday morning collection routine.
But I think the lads who operate a cheque system, who finds it work for them is the best; obviously.
It must be a matter of 'educating' your customers. Could be a new thread in there somewhere.