Have to say 24hrs. That way if you are over tired and as a result can't sleep you can watch tv for a while until you do pass out. On a 12hr layover when you cant sleep you get worried about being to tired the next day.
Thats just my opion.
Also seen your name on pprune for a while and I am wondering about why you called yourself Ironbutt57
. Is that because there are 56 Ironbutt's before you out there????
No offence intended just wondering.