The Collector weighed the elite specimen Goromir's suggestion. Notably, the elite only said it had 'hope' that the Amoraks would aid the Collector, thus it was not an assured guarantee. Yet, the Collector could certainly make it closer to a guarantee.
By reviving the Amoraks, the Collector had their lives in its hand. The Breath of Life functioned by growing regenerative ice crystals from the Collector into specimen, and these crystals formed new body parts and internal functions to sustain the revived specimen.
Which meant that at any given time, the Collector could simply recall the ice crystals into itself or cease to fuel them, causing them to melt and consequently return the Amoraks into true expiration.