The Original Star Ocean can be beaten in about 20 hours. Now that I do give it a second thought - As long as it has the typical post game content and that true blue SO grind.... I dont care. The idea about there needing to a certain length designation is just as bad as pixel designation.
What about the other star ocean games? 40 hours or more of gameplay is the standard length of gameplay in a rpg. If anything the standard is getting longer for most rpgs. It just means there's that much more content to play through versus there being less.