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.
"He who defeats himself is the mightiest warrior" - Confucius(I think)