I've got a lot of palm and needle whippings on my boat that are 20 years old or so, and have yet to see one of them fail. Some of the simpler wrapped whippings have come apart, though not often. Tension and a bit of wax would probably help them. For expensive/important lines, I'll even put two palm and needle whippings on the end (one at the bitter end and another 3 or so diameters in) which will probably never be needed, but looks damn salty and heck, I enjoy whipping, splicing, etc. If you're working with 3 strand, you can also do a sailmakers whipping which is just as secure as the palm and needle method, but doesn't require a needle. Good palms and needles aren't sold at most marine
stores, and make the job a lot more pleasant. Your local sailmaker
should be able to set you up with good needles (take care to store them so they don't rust.) Palms take a bit more hunting these days.