My Scorch/Fire Genin will earn these eventually at Chunnin or Jonin, the time limit is one post. And using the ability requires lots of chakra, to surround the body, go at very fast speeds, and try to cushion strain as much as possible. The strain of all the Gekirinkens (minus Mental Gekirinken) are huge and shouldn't be used more than once a day. Think Primary Lotus strain but a lot more.