The 8th level power of rune domain gives the ability to place the runes on doors, chests, etc. It says the rune triggers when the item is opened. Does the rune only last for 1 round per level as it does when placed on an open adjacent square or does it last until triggered?
Good question. The fact that the rules say "You can also place these runes on doorways, (...), causing them to TRIGGER when a creature opens the object" seems to imply that only the triggering condition changes (opening the object instead of merely approaching the Rune itself); since there are no specific conditions about changing the duration (as opposite, for example, to the Artefice 8th level power, Creation, that specifies different durations for different materials created), it seems that the duration itself of the Rune stays the same, 1 round per caster level or until triggered.
But I admit that it's not very clear.