Well, if FFXI could last ten years on a stand in one spot and mash buttons to grind for about 200 days of your life so you can do the cool stuff, then FFXIV will be fine. I loved FFXI, it's my favorite of the FF titles, and i withstood the grind for all the great things that it had more than that ... so things like achievements or general content. A level sync with good reasons for players to revisit, and some uber hardcore items like relic weapons etc. Add enough content to LS houses and building as well. PVP has a kind of longevity to it that PVE never achieves as well. Should be fine.