i longboard half the time and i dont use a leash on a longboard even in bigger surf i mean if you need a leash on a lb in 6foot waves you shouldn't be out on one, but with all my shorts i use dakine and have surfed them in all kinds of surf and haven't had one break yet.
All leashes suck. I have broken pretty much all of them. I can't get more than a year or so out of them. I think when I lived in CA, i got a little more life out of them just because they have been used every day and it prevents rusting maybe, but I have broken 2 leashes in SC on sh**y days in the past 6 months. The shelf life on leashes these days leaves a lot to be desired, and its always the swivel piece that breaks, although I have had an FCS on that broken in Mexico the day I bought it and it snapped right in the middle of the leash, about 3 feet between the top and bottom. But my disclaimer there is that I bought it in mexico, because I snapped a good one earlier that day. 2 leashes in one day. First was Dakine, second FCS
But I have had bad luck with them all. Creatures of Leasure, FCS and Dakine... crap leashes.
I use a Dakine on my fish and WRV on my longboard. No worries for a few years. However I've learned that taking good care of them will make a difference. When not in use keep them straight not wound up. plus dont wrap them around your fins.