The shortest by far is a referral partnet or mine who wants the bill sometimes even before I go out to test a property and will pay before the work is even done. I even try and get them to not pay until service is given just in case a unforseen problem comes up that prevents me from getting to that job on that day. They say it is fine, they know I will get to it eventually. And because of their confidence, I do.
The longest are those open invoices that I know will never get paid. I place too much trust in the person and agree to just send them an invoice and they promise they will pay it as soon as they get it. Unfortunately that does not always happen. I feel a bit suckered everytime. You would think I wold eventually learn my lesson.