I kinda love it and hate it. They're not all the same.

You often see particularly tactical battles ending with both guys basically purging all their energy in the 12th, which I don't mind (infact I quite like) but there are some fights where it goes way beyond tactical and the fighter(s) are just plain cautious and so then it just appears that suddenly a degree (very rarely most) of that caution is lost for the final 3 minutes. Which definitely sucks because indeed as TitoFan said ''If you had it in you for the last round, you should have brought it out BEFORE then''

Of course then there are the real-deal big 12-rounders where fighters literally FIND the energy after an exhausting and gruelling battle.