User blog comment:B214/Question and Answers/@comment-24098614-20131103045517/@comment-16281343-20131103050834

The Nekoshou's lifespan is irrelevant right now since the only known members are devils.

I think the manifestation or appearance of the 2nd tail is due to them using senjutsu.

And with regards to the appearance of Koneko's 2nd tail, it is called Nekomata Mode Level 2 which gives her explosive power for a temporary time.