VII was about 70 hours

VIII I cant remember , probably more, Id guess about 80/90, Im nmost displeased that there isn't any save data for VIII on my memory card....

IX just shy of 100

X the file that ive almost 100% apart from a couple of dark aeons and penance is 140 hours

XII - 163 Hours gotta complete the bestiary and Yiazmat before Im done there, so I reckon Ive a fair few hours to go on that

Soo I cant really say, it's dependent on the game, I know I spent roughly 40 hours on each game from I to VI but I couldnt give an average for this lot really