How long does the temporary shielding last, not in terms of games but in terms of time?

I was recently promoted to Diamond V in League of Legends. I have heard that you are shielded from being demoted the first 10 games. However I was wondering how long the shield lasts, not in terms of games but time-wise. What I mean is whether there is a temporary time-frame where the shield expires regardless of how many games are played (ex: I play only 5 games in a 28 day period yet the shielding expires due to time) or whether the shield acts indefinitely until you play the 10 games (ex: I play once every 3 weeks and the shielding applies until I hit the 10th game even though it has been months after the promotion). Thank you very much.