Specifically from the CRD:limitWhen a card has a limit, such as "(limit +3)," the limit applies to that card for an entire phase.
Trust Me As You Once Did reads: "Skirmish: Exert Gandalf to make a companion strength +1 for each
companion with the Gandalf signet you can spot (limit +3)."
With one copy in play, assuming you
have sufficient signets and exertions, during a single skirmish phase:
• You may add +3 to one companion in a single action (if you can spot at least 3 signets).
• You may add +1 to three different companions in three different actions (if you can spot only 1
signet).
• You may add +2 to one companion and +1 to another in two different actions (if you can spot
only 2 signets). Once the limit is reached, no more may be added, and the last +1 is ignored.
A limit does not does not span multiple phases.
Trust Me As You Once Did could be used for +3 in each of two or more separate skirmish phases during the same turn.
A limit does not apply to a different copy of the same card.
With two copies of Trust Me As You Once Did in play, you could give up to +6 in strength bonuses during a single skirmish phase (+3 from one copy and +3 from the other).Just in case someone wanted it from the rule book.
-wtk