Thats a good one but yeah checked out there feats on the marvel site, iron fist uses chi and when he uses the iron fist punch they reckon he becomes weakened or drained and takes him to to regenate himself with energy /chi as he has to meditate for a while to restore his energy, saying that maybe sabertooth will get the advantage coz later he becomes a bit like wolverine gets the adimantium in his bones and his healing and regerating factor is fast so he might just get the better of iron fist,but then again if iron fist uses his martial arts he can dodge all sabes moves and hence get the advantage over him,but then sabes will heal quick etc.. so probably iron fist just if he fights smartly which he does
Against Panther, he kept busting out charged punch after charged punch, with a large aura of ki all around him the entire time, shredding his vibranium suit.
No idea how long he can keep it up, but the days of tiring out after only one to three Iron Fist techniques are gone.