That was also like 500 BC when boats were super fucking shitty, and most D&D settings have sailing tech at least equivalent to Age of Exploration stuff.
It took Christopher Fucking Columbus less than three months to cross the entire Atlantic ocean in 1492, a journey of over 3,000 miles.
That's patently untrue. A Nat 20 is only a guaranteed success on a saving throw or an attack roll, and that's regardless of whether there was any chance of success.
Nat 20s don't matter on any other checks, unless you house rule it in.
And that was an entire campaign, and such a ridiculous amount of time his name is the root for ridiculously long voyage.
Everyone else got back faster, he literally had the god of the sea personally pissed at him in specific.