I've only been playing for 11 months, but at this point I can't really see myself reaching burnout. Not saying it'll never happen, but I'm at a point where it still feels as if I've barely scratched the surface.

However, I should probably note that I came to FFXIV due to very much burning-out on the MMO I played before FFXIV. I'd played that one for over a decade, but ended up quitting last December due to a combination of powercreep ruining the gameplay and a sleazy business model with an overwhelming dedication to using FOMO and gambling/loot boxes and expensive (£300) item 'bundles' to to strip-mine their player base for all they can manage, with absolutely no regard whatsoever toward sustainability, burnout, or player feedback.