We have used Star Alliance to book several trips a year -- started when EVA officially joined the Club. Mrs. always flies on royal laural class, JFK/TPE/JFK route, with additional Bkk stop at times.

We have the most success with last minute bookings, which I realize doesn't help OP out. As far as we can gather, Eva doesn't seem to have a hard fast rule as far as we can tell. There is more discussion in this thread: http://www.flyertalk.com/forum/other...ence-here.html