I've had a set of DIY straps fail due to weak thread. I was using polyester thread but it was a spool for clothing. Once I realized my mistake, I switched to my gutterman thread and havn't had a problem.
I've been using some amsteel now that is a few years old and it is still going strong. I recommend always inspecting your gear prior to any hang to check for damage and fraying. Replace at any sign of wear that makes you uncomfortable. Err with caution. Never hang any higher than you are willing to fall.