This in particular has tripped me up. I had a relationship with a client that took 45 - 60 days to pay, but they always paid. Things were great for over a year and a half, they had tons of work for me and I made good money. Then all of a sudden 60 days became 90 days. At that point you have already filed a few invoices before you sense a problem and cease work (I was sending them in every 30 days). Basically they went Chapter 11 owing me over $10k - of which I was only able to recover 30% after being very, very persistent with their lawyers.
Sure, I am sure if it ever happens to me I will feel different. All of my client now have been with me 3 to 5 years. I have never had one run past 60. I am not saying that it could not and is not going to happen, but I feel pretty comfortable with my clientele. Most are fortune 500 public companies so money troubles would be in the news long before they where set to implode.