Weather wise - of course the further you go, the more perfect the weather must be.
Fuel wise - it's just math...
You must know, and I mean REALLY know, what your boat burns at cruise with a heavy load (ice, full fuel, full water, gear, guys, etc.). You must also know what you burn while trolling.
Then, understand what ever your fuel capacity is, multiply that by 90% (95% tops) as that is what is "available" for use since you can't get every drop out of your tanks. Then multiply your "available" fuel by 65 or 75% to allow for a safety margin - in case weather comes up and economy goes down or you decide to alter your float plan by running further out or staying longer.
Having a good supply of fresh water should not be overlooked when running far offshore. And water weighs basically as much as gas so the weight all adds up. Lastly, I would not venture over the horizon without two engines on my transom but that's me. Good luck and I hope some of my suggestions here makes sense and are useful to you.