Packet over SONET failback

PoS failure detection happens in under 50ms, but what about the failback? Same deal? I ask because I've got two routers connected to opposite ends of a spare PoS link that I've been playing with and I'm noticing that the failback on the far side seems to be about 15 seconds (assuming the near side failover was initiated with an interface shutdown command and thusly no shut'd to re-enable the link). Just wanted to know if a higher failback time is a relatively normal occurrence and maybe I'm seeing some sort of built-in hold down feature working away?