Say you had a wizard under the effect of Contingency so that if he died gentle repose was cast on him. Would a cleric with breath of life be able to come over at any time even after more than that one round had passed but not after gentle repose had ended?
You preserve the remains of a dead creature so that they do not decay. Doing so effectively extends the time limit on raising that creature from the dead (see raise dead).
Breath of life
Unlike other spells that heal damage, breath of life can bring recently slain creatures back to life. If cast upon a creature that has died within 1 round, apply the healing from this spell to the creature.
Yes I know that breath of life has a specific condition of 1 round. But gentle repose also has a specific condition in which it extends the time in which a creature can be raised from the dead (which does also mention raise dead). But in this case would breath of life work on the dead character?