3+ hours is plenty of time to shower and Eat. I would absolutely not stay longer in the airport just for the long-haul seats, even if they were more reliable than reported. It's a 3 hr flight to SIN and the regional J should be fine. (Admittedly I haven't yet been on new regional J, but the old regular recliners were perfectly comfortable.) they're better than anything you'd normally get on a 3 hr flight within the U.S.