So the timeline of events in the game always interests me, and let's be honest, the 'ever expanding bubble of one year' is the weakest argument ever made, especially since it directly conflicts with several other sources about travel times.
As such, I think it can be said that the timeline of events, more or less, can be contained within a 3 year period, perhaps a little less, but no smaller than 2 years.
Year 1: Realm Reborn and Heavensward
This is the one that is the 'stretchiest' in many ways, the events of Realm Reborn likely took several months, but we know for a fact Heavensward must have played out over some time between 3 and 9 months, because a woman you encounter during the questlines goes from pregnant with child but not showing to having given birth to that child.
Year 2: Stormblood
By far the biggest hurdle to the idea of 'everything in the main quest happens within one year's time', due to the travel times between Othard and Aldenard. Even if we assume airship travel is significantly faster, airship travel was not safe until the later patches when the Garlean Empire began to fracture and fragment, so we're looking at a several months trip both ways by ship, and you definitely, in the story, took one trip yourself by boat.
Year 3: Shadowbringers and Endwalker
Of all of the expansions, these are by far the most flexible. Endwalker involves a place where time dialation effects are occuring, and so what might have taken weeks, months, even years in the First could have, and probably were, only bare weeks in the Source. For Endwalker, by far the most globe trotting of the expansions with how much and how far the player goes, the distances involved are all covered by air or by magical teleportation, with the sole exception of the march into Garlemald itself, which was ostensibly done via well maintained garlean roads between the capital and through some of their most developed, but by that point, least defended lands, as all of the armies in those regions had pulled back to take part in the civil war, thus leaving a big gaping hole through while anyone could travel relatively unopposed.
Anybody got bits or bobs to add to this theory?