I reckon I could beat the storyline in like 30 hours, It's not really that long and once you get to Bur Ominacence (Sp?) The games pretty much a breeze.

Get the zodiac spear as soon as you can (which isn't to far into the game)
Chain level with Dustia, cuts time down dramatically.

As for 100% completion, I have everything, all Chars level 99 and My game time is 124 hours 57 minutes.