Infinitely? Well lol not sure about that, but yeah at least up until Vashjr/Hyjal, you have a choice where to level up, something this game really should have, especially with 14 planets/50 levels. Not sure why they didn't put in parallel paths, hell you can't even do all the quests on each planet or you will completely outlevel a planet in short order.
So yeah, Bioware please keep this in mind for the future and allow alternate/parallel paths.
Lastly, on an unrelated note, someone was saying with a straight face here yesterday that WoW was a sandbox mmo...