Should the authtoken be cached accross sessions?

It's not totally obvious from the login guide whether the authtoken is meant to be cached for the current session or whether it's meant to be cached long-term.

I'm keen not to get my app blocked by blink, so want to act in a way that is likely to be acceptable!

I am aware that it might be possible that no one in this community knows the answer, but thought it was worth asking here.