One of the rules of plastics is that they all degrade in sunlight. The nets on my 40′ x 36′  trimaran seem to be the exception to that rule. My Net Systems knotless black polyethelene nets have been flawless for some 15 years. They do need to be tightened every season.
I give them the leap-off-of-the-hull onto them every so often to impress the crew. I recall the failure point some years ago during the Shaw Island Classic when Mark Evans leaped into the net. The cast padeye holding the net exploded.  Many thumbs up on this product.
http://www.net-sys.com/catamaran-netting.php