Are five-round main event non-title fights good for the UFC?

On the one hand, it would seem obvious that an extra two rounds would provide more time for closely contested fights to decide an eventual winner.
On the other, training will become more difficult and in turn, injuries are more likely to occur. Lord knows there have been enough injuries to last a lifetime.
On a recent episode of Inside MMA, Chris Leben (who will participate in the first five-round main event non-title fight against Mark Munoz at UFC 138) and Melvin Guillard gave their take on it. Here's Leben:

"Five rounds, you want to know how I feel about it, sucks. I'll be honest with you, I'm not stoked on the idea. But this is what we do, this is my job and this is what allows me to move up so I'm going to do what I gotta do."

And Guillard's take:

"I'm one of those guys, I'm a finisher. Training for five rounds will probably be the worst part of it. But actually going five rounds? I doubt if anybody fights me (it) goes five rounds. I think the good thing about it is that it prepares you mentally for a title fight. A lot of us, I haven't been in a five round fight. So when you step up to the stage and possibly after I knock out Joe Lauzon, they move me to number one contender or title shot, I have to fight a five round fight. I don't go into a fight thinking that I'm going to go the distance or going to finish it quick but it's good to be prepared."