I'm not saying 1.7K a week, but they aren't keeping on top of the PRs being raised so the number just keeps increasing, unless bots just close them because of inactivity.

At some point they will have to cut their losses, strip back to a week's worth of PRs and close everything else to get back on top (perhaps this is actually what is happening, it just takes the bots a while to chug through them).

Edit: just checked and it's now 1.9K PRs.