That 10 Game Shield after winning your Promos and entering a new Tier. How long does it last?

I think I read somewhere that it's 28 days?

But in this case, is it all gone by 28 days? Or do they disappears after 28 days of inactivity?

What I mean is, after 10 days and I play one game, does that 28 days reset and I get more time till they go away? Or will they all still expire by the 28th day regardless of how many of those 10 games I play?

Or does it even expire at all? I might be going on vacation in the upcoming weeks, and I've been busy lately to commit a full hour lately, but I only just got promoted and I don't want to get demoted so soon after reaching such a goal.

If the 10 game shield goes away based on inactivity, I can just play a game shortly before going on vacation, and then comeback with the shield still intact hopefully. If not...c'mon...

(this is why prizes should be awarded based on your highest achieved rank and not current rank!)