Limits and Maximums
“Limit once per X” is a limit that appears on cards that remain in play through the resolution of their effect. Each copy of an ability with such a limit may be used once per each period of X.
The Emperor’s Champion
Combat Action: A target ready enemy army unit at this planet must be declared as an attacker and this unit declared as a defender during your opponent’s next combat turn, if able. (Limit once per combat round.)
Combat Action: Discard a Warrior card from your hand to ready this unit. (Limit once per combat round.)
Are triggered abilities with a limit able to be initiated unlimitedly outside of their limit period? For example, suppose Talyesin's Warlocks commit to planet 1. May they use their combat action in the action window before the battle at planet 1 and then once again during the first combat round? Similarly for The Emperor's champion.
Not related to the same restriction, but interestingly if either of them are at a planet other than p1 where a battle will take place, they can use their ability at least once during the last combat round of the planet 1 battle to effectively have it happen twice during their battle's first combat round.