I think that Sidious overestimates the strength of the storyline fights. I just fought a storyline boss last night (after doing hunts for about the last 6-8 hours) and it was complete cakewalk. I mean he basically took away all my MP so he wasn't allowed to be too hard, but the hunt I did right before him was about 5 times harder. In addition, equipment in this game boosts your stats at least on par with leveling and since that is directly tied to your place in the storyline, your characters probably get stronger faster. Still 40 might be pushing it, there's a lot of walking (Lord of the Rings style), but I think you could do it a heck of a lot faster than we are. Still I don't think it's too long because I am constantly seeing new things, getting new stuff, fighting new monsters, and there are still plenty of areas I have encountered that I am nowhere near strong enough to traverse. As I said, as long as there is content and gameplay to back it up, length is a good thing.
Hey Incog, I'll probably call you about this, but if you see this post first, you up for some Gears Multiplayer tonight? Let me know!