Does a card turn face down automatically when its 'as long as this card is face up' effect is no longer needed?

Question

Accepted Answer

No. Cards turn face down only when a Villain, Hero or Threat says so, such as Modok or Rogue. Otherwise they stay face up, and a card can leave the Storyline when a Hero trades it away.

Marvel United: X-Men

Does a card turn face down automatically when its 'as long as this card is face up' effect is no longer needed?