Icy Prison - is the duration correct ?

[Cathlessra]

Icy Prison has a duration of 1 min/level. As a level 12 caster, I imprison a creature for 12 minutes in 12 inches of ice doing 12 cold damage per ROUND. If the creature doesnt break free (DC 27), it will take 1440 damage.....I'm wondering if the duration should be 1 round/min (as the spell cannot be dismissed to free your prisoner and interrogate him/her/it)

[Drakkiel]

If you happen to catch a single enemy...alone...and he fails the save...then yes he's gonna die

If not then

1. His buddy/minions can break him out easily...at 12th level the ice only has 36 HP

2. He is only entangled and can break it himself