I had heard they were soft on when the 8-year period starts. Though the scheme came in 2003 (so the first upgrades started 2011), they were upgrading people before then - eg people who had been gold since 2002 could get upgraded in 2010. But they were strict about the broken periods. (I was in the category too - 10 or 12 years as gold, but 1 year as silver 2002/2003.)

I wouldn't call them. Sounds like an IT issue or perhaps they've widened the net.

Yep - no real benefit for a PL flyer of Diamond over Gold. All I can think of is:

1) guaranteed availability if you book 72 hours ahead (and more likely to get a seat within that period)
2) use of the Garden at TPE (but not really EVA's "top lounge" anymore)
3) Use of "diamond check-in lounge" at TPE and Songshan.
4) take a companion into a non-EVA lounge.

Of course you can transfer upgrade vouchers/miles to friends.

I think the lower the class of travel, the better the benefits of having status with EVA.