Eternal Guard should be getting their buffs on a turn in which they're charged, as Form Forest of Boughs and Forest of Boughs state "in the same turn". Your opponent's turn is a separate turn to your own! With that in mind, situations in which you lose the bonuses are functionally: 1) If you move (including retreats) in your movement, 2) if you charge in your turn, 3) if you make a pile in move in ANY turn.