The old metal-to-metal needles and seats would wear out to where they would leak - not all that unusual. The newer ones with the polymer or synthetic needle point simply don't seem to have wear issues. The biggest reason for leaking at the inlet that I have seen has involved some kind of stuff which prevents proper seating. The tank has curlies left from machining the openings which can be a big problem if you don't keep a filter inline. Sometimes you can also get sediment in the fuel if it is drawn from a steel tank which has rust sediments in it. Those can find their way through some filters. I suppose it would be possible to wear a hole in a float if the machine has seen lots of rough miles and hard riding. I can hardly imagine that though given the many tundra miles we've put on machines without it ever happening.