"Brand expires" meaning

Hi!

Recover 10% of Mana when a Brand expires while attached.

Let's say I use Penance Brand.

What exactly does expire mean?

does it only refer to the duration or does expire also mean when it explodes due 20 energy reached and the explosion occurs?

When I "overcast" and exceed my brand limit I think a new cast means the earliest brand around is lost, does that also count as expire?

Thanks!