Cult Ambush Markers Rule

Hey all! have a question RE our army rule:

Units in Cult Ambush
Cult Ambush is a type of Strategic Reserves. Units in Cult Ambush cannot be targeted with the Rapid Ingress Stratagem, but can be set up on the battlefield using a Cult Ambush marker as described below, or by following the rules for Strategic Reserves in a subsequent turn. Units in Cult Ambush are not automically destroyed at the end of the third battle round.

Cult Ambush Markers
Use a circular 32mm diameter marker for Cult Ambush markers. If an enemy model (excluding AIRCRAFT) ends any kind of move within 8" of a Cult Ambush marker you placed, that Cult Ambush marker is removed from the battlefield. At the end of your opponent’s next Movement phase, for each of your Cult Ambush markers still on the battlefield, you can select one unit from your army that is in Cult Ambush to make an ingress move. For that ingress move, set that unit up with at least one model in that unit in base contact with that Cult Ambush marker and all other models placed wholly within 3" of that Cult Ambush marker (that Cult Ambush marker is then removed from the battlefield). Units in Cult Ambush can make an ingress move in the first battle round using this rule.

My play group are questioning if Im I choose not to bring my units in cult ambush during literally my next opponents move phase if I am then unable to bring them back on a subsequent opponents move phase? My understanding is you can choose to bring them back or not, but get to make that decision for each cult ambush marker on each of your opponents move phases.

Can someone give me a rundown on what is actually expected as I’m not 100% clear!