I can't remember anyone having failure of hammock strap or line material, even when we were using yellow polypro and tying knots in it. I think the rated strength of that braid was < 500 pounds.
Knots have failed, splices have failed, thread has failed. Hammock material has failed.
I have had yellow polypro break with other uses - but only when it was left outdoors in the sun for long periods - greater than a year. UV degrades many of the materials.