yeah i think cause he doesnt have to do much
a few hours might have passed as kakashi moved from where he was exactly fighting the sword folks, so we might assume he took a break. Maybe too, he´s just evolved his chakra limit as most of early characters have too.
Even Tenten is able to use one of the rikudou senin war tools, so...(and that`s a f_cking big statement)..knowing d fact Tenten is like an ant in a farm when talking about chakra.
aNYWAYS..my thoughts