isildur didn't have the ring very long when he went to destroy it with elrond. But humans are weak, i don't know if a hobbit could have done it in his place. So my point is the time might be a bit irrelevant.
Frodo couldn't throw the ring in anyway, Gollum fell in it by accident with the ring. If they didn't walk they would'nt have gollum chasing them and then the ring could not have been destroyed. if they flew with eagles, sauron would regain the ring or either frodo would have kept it for himself for a while and then get captured.
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