Some things I observed tonight in terrace:
Using AE on hidden Lei Shei refreshes your AC stacks.
Stacks still refresh from AE on the Sha adds even though it says deflect.
And unrelated to terrace, but in general, if you have to move and are in danger of losing your stacks, and have a missles proc, stop, cast missles, then move super quick will count to reset your stacks.
These of course might have already been mentioned.