It keeps things fairly in check, but it depends on the route FF14 wants to be(assuming it has a future next year).

Do you want a game where a population is spread like old school games like FF11, everquest, etc. Where you have a large portion of "feldgings" and "verterans" and only a small portion of "elites" aka end-gamers.

OR

Do you want a game of majority of end-gamers and very few of the rest. Much like the rash of new MMO theories since WoW and the "PvP" groups.

Caps have to raise fast when you deal with endgamers, but rarely have to be raised much for adventurers. 1-2ys sounds like the oldschool method, where you are only raising the cap to keep the elite, elite, and let everyone else move at a normal rate. A good average is usually around 10-15% elites, as a "stick dangling" effect to a game, where the feeling of "glass ceiling" will not arise.

FF11's "glass ceiling" effect was getting much too heavy due to this, and reason why lvl 99 was a little late. Too many people were at the top leading to many unpleasant effect.

WoW's is why you have so much stupidity at the top because everyone is fighting for that rare of rare piece...because there was nothing else to do, and much too many people wanted it. Content became incredibly finicky as it almost always has to catered to endgame and endgame only...because everyone was endgame.