I may be wrong, but I think the official time is still 3 months from date of deletion before things get sketchy. At least, that's the official word from S-E (
link). I had a rl friend contemplate coming back to FFXI after a year long absence, and his information was still there (this was during Return to Vana'Diel 06); he ended up not coming back...the call of WoW was too strong for him to deny. But anyways, yeah, one year later his chars. we're still there. As for items, job levels, etc...not sure. He only confirmed it was even possible before he decided not to start playing again. How he did it, I don't know...I ain't cancelling my shit until I know I ain't playing no more. I worked too hard to take a chance.
My advice to you would be to keep it under the 3 month mark. For all we know, you could cancel your acct and come back in 5 years and have it work (if the games even still being played, then), but if you ARE planning on coming back better safe than sorry.