i think it's very possible, albeit difficult to balance RL in the form of either job or school (both would suck, but it's being done as we speak) with FFXI. there's only a handful of people i know outside of hardcore JP LSes on bahamut that dont have a job or school, and yes they can play a ton. i've been in college since before i started playing, but my first semester playing i raped skipping class and sort of pwned my grades. i got to 75 though waffles. it's unsustainable, for how long varies from person to person, but people who do it for a while get pretty far.
anyway, since then i've either had a job or school and i've gotten a ton done. i think it takes a lot of foundation work (leveling up, growing together with an LS, skilling crafts) which goes much faster @ a haijin lifestyle to be able to back off and play a little more casually.
anyway, i try to steer clear of avoiding RL attacks because i'd be making fun of a lot of people i know (including myself in some ways) and it's up to people how they manage their RL time. 62 in 7 months is slow, but still, at least youre getting somewhere. when you're 75 you'll be able to enjoy playing casually a lot more imo.
saying everyone who's successful in the game has no rl friends and no job is pretty inaccurate. over the long term it all comes down to time management, because theres people with poor management who suck at the game and have no job/school/social life.