I don't really get this obsession with people keeping their gear. I mean, after you have your uber gear what do you do with it? Get even more uber gear. That is one of the big points in MMOs, your continuous progression.
Well for starters, FFXI for the most part doesn't have straight-up 'best gear'. There's your baseline endgame gear, and then there's a multitude of situational pieces that each benefit a different gear setup. Keep in mind, in FFXI (and presumably in FFXIV) you can macro in and out gear mid-combat. You're not locked into your gear until you're out of a fight. So you can use a mix of Accuracy and Attack and Haste gear to increase your standard DPS with some extra DEX+ or Acc+ if you really need it for high-evasion mobs and Atk+ and STR+ for high-defense mobs, then use stat+ gear to cap out damage from your weaponskills, while also having an Auto-Regen gearset to minimize downtime and make your healer's job easier.
That said, once you have the gear you want, you use it to contribute more to your groups when you work together to complete the difficult missions that the numerous story-driven missions have.
After all, that's what's most important in an FF game. The story.