How long would it take to circumnavigate the minecraft "planet"?

If I had a very long stretch of powered rail going in one direction, would I be able to eventually circumnavigate the planet? and if so, how long would it take?

(Assume the track is entirely flat and I burrow through all mountains I hit)


Minecraft subscribes to the "Flat Earth" theory. Discounting mods, you can never circumnavigate the planet, as the "planet" will simply expand longer and longer in whichever direction you travel.