It’s a monumental achievement! Arcane Shields are finally purchasable for glory… wait… /sigh
So, when exactly was the last time Arcane Shields were purchasable for glory? Let’s look at the past release schedule for Blue/Brown troops…
Going backwards in time (credit: the Event Spreadsheet; ignoring mythic troops as they aren’t tied to events),
Week of September 24, Halfgrim Half-Giant, Raid Boss troop, nope.
Week of May 28, Sir Wulfrik, Invasion troop, nope.
Week containing March 16, Ice Wraith, Bounty troop, nope.
Week of January 1, Chief Stronghorn, Legendary, nope.
Wait… we have go back to 2017 for the last time Arcane Shields were purchasable? Yup!
Week of October 20, 2017, Leviathan, Legendary, nope.
Week of August 14, 2017, Forest Troll, YES.
So, dropping those dates into Excel for a quick time calculation… at the start of the this week’s event on the server day change, it will have been 406 days (and counting!) since the last weekly event where Arcane Shields were purchasable. 
Yay, for a new GoW record!
And according to the spreadsheet, there’s currently no event troops for October that use Arcane Shields either, so November is the earliest (short of an unplanned change to the event schedule) for this streak to be broken.
How long can this streak last? Place your bets, everyone! Over/Under, before the start of 2019?