I'm against this. It will put fighters with great conditioning in an advantage over the less conditioned but more explosive or technical fighters. The pace will be slower, the fights will be more boring. It will ultimately lead to battles of attrition instead of battles of skill.
Instead I would allow an extra round if a fight is too close to call, similar to K-1 system.
I have two questions then.
1) would you rather title fights be 3 rounds then as well for the reason you listed? Why should a fight be leaning towards the fighter with great conditioning simply because it is a title fight?
2) Wouldn't you say that conditioning and strength are kind of two ends of the spectrum? The guy that is more explosive usually sacrifices conditioning and lasting power for the ability to finish the fight in the first round. To me, each fighter gears himself to how he wants to fight.