So, it took me a almost a month and a half but I managed to recover from a 3 month hiatus and a backlog of 2400 reviews.
Thus - my message is - do not despair.
Life happens. Circumstances can get in the way.
But if you truly have the goal always in front of you - then as long as you’re alive you can always strive to continue moving forward, despite any setbacks
Very similar picture for me, below. It just happened a few levels later than yours. I’m intentionally targeting slower level-ups now.
I intentionally decided against vacation mode, and I stand by that decision. I don’t want to artificially extend my timers. Dealing with a wall of content feels bad, but the good feeling that vacation mode brings is artificial, because the “empty review pile” you’re looking at actually includes things that are truly overdue, but do not appear so, because vacation mode messed up your SRS timings. And now you’ll be tempted to learn new things, rather than tackle those old overdue things (because you’re not even allowed to tackle them yet, because of your choice to use vacation mode).
And I just learned about the heatmap widget from your post! Including below as well.