I do not recall my first triple cart in MH1 since it has been so long but I can easily say that Barroth was my first in Tri and I have yet to triple in 3U (1/2 way through 5 star village quests). I swore I was going to triple cart on Duramboros though when I was trying to learn how to use the LS. But, as the fight progressed so did my skills with the LS. I didn't even end up carting but went through 8 Megas.
I only double-carted on the first Pink Rathian. I was stunned when she clawed me and right when the final star was fading she engulfed me in wyvern fire. The final cart was when, again stunned, she raged me into a corner... I was so under prepared, but I killed her in a few hits after the second cart. >_>