Theoretically I could run the Drowned City of Skalla forever and never get the fending coat.

Theoretically I could send my retainer out forever and never have them come back with the special untraceable onion helm (the one you only get from them, not the other one).

Theoretically you could never get the special ring for getting 1st prize at the jumbo cactpot.

Man ... Thinking about it there are quite a few things we do in FF14 that do not guarantee the reward you're shooting for. In some ways that's scary, but in others it helps some activities (like fishing) feel kinda "at home" for me.
But I got the fending coat.
My retainer brought back that helmet.
AND YOU CAN GET THIS CHEST!