I would want more (6 hours more), in college i was on a 20/10 schedule (awake for 20 hours then sleep for 10 hours),this is my "natural" rythm. On a 24 hours day I am never tired when I need to go to sleep and very tired when I have to wake up. On a 30 horus day I went to sleep when i was tired and woke up fully refreshed every day.
I think many people will misinterpret this question thouhg thinking that having 2 more hours means they would get 2 more hours of sleep or 2 more hours of watching TV. You have to assume proportions stay the same though. Like for me my current day is 12 hours at work, 4 hours of other stuff and 6 hours of sleep. On a 30 hour day that would mean 15 hours of work, maybe some people wouldnt be able to handle that.