I started playing in November with a friend of mine; we used to do warcraft or starcraft lanparties, so we tried doing an FFXI lan party. Didn't quite work out, but we decided to keep together and keep going.
She got into a linkshell of major powerlevelers - started as the NA offshoot of a JP shell - and I bounced around a couple until I settled on a decent one given to me by a higher-level JP player. We kind of separated, chatted once in a while online, but never really played together.
Now, I'm a thief. I've been a thief since I started - and I'll take THF to 75. I play a couple of other classes, but I've only got 4 leveled, and only 2 are over 20. Part of being a thief to me was the whole silent/invisible/creeping around aspects, so I bought silent oils and prism powders and started looking around.
-- and have never stopped.
This game has so much more in it than levelling; yes, levelling is required for some of it, but it is a means, not the end. There are so many areas, so many monsters, so much to do and see that most people never seem to miss before they hit 75 the first time.
I'm in a linkshell now, started with a close group of friends. It's not large; there's only 2 or 3 of us on at a time, usually, and sometimes not even that. We're very spread out in level ranges; we're very diverse in our play styles. But we're friends, and we talk, and it makes everything more fun. Yes, we cheer when someone "dings" a new level - we also cheer when someone gets a new craft level, or finishes a quest, or finds something totally cool that they'd never seen before.
And, yes, my friend is one of the people in our shell. So is the Mithra I helped to get Dragoon - when I was only level 28. So are a few people we met doing Rank missions, or Eco-Warrior.
And, sometimes, when parties are slow or there's "nothing to do", I'll go explore an area, just to see what's out there. And sometimes they come along
The Road goes ever on and on
Down from the door where it began.
Now far ahead the road has gone,
And I must follow, if I can.
Pursuing it with eager feet,
Until it joins some larger way,
Where many paths and errands meet,
And whither then? I cannot say.
-- J.R.R. Tolkien
Good luck and good hunting.