if it had auto log out / auto dc then i'd want it to have a fairly generous time frame maybe 12 hours....

in 12 hours i'm almost certain to have any repair requests completed or any meld requests done. so yeah i wouldn't mind being booted from the game...

anything less and i'd start to have problems with it. there are time's where i'll sit afk in uldah playing my playstation simply glance across to my pc every 20-30 minutes seeing if there any interesting shouts if not carry on with playstation. so if i would be dcd after like 1 or 2 hours then i'd start to have problems with it.

i will tell you one thing i would use alot though... (pretty sure it'd be tricky to implement)
auto-return/logoff when repairs/meld requests are complete.

that i would find fantastic. finish my event or whatever i'm doing put my gear up for repairs and go to bed.
when some nice person repaired all my gear and/or did all my meld requests my character would aytomatically return to my inn room and log off.

i would bloody love that