"hese poi wear the leashes out before the wicking does"
and at $60 I'd say that you'll have to replace the whole poi everytime they die instead of just the heads.
Nice concept but there's far cheaper and better methods you could employ to avoid exposed metal if you really keen on wrapping all the time.
I'd suggest making your own, it's not that hard really. You could just tie monkey fists into the end of 1/4 or 1/2 inch rope and spin those

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Becoming a Dad is the best feeling in the world

Watching them grow teaches you a whole new type of love