Improve rate limiting

[wnelson03]

I feel like I remember the old version (the one you pasted in DevTools console) better adapting to rate limits;for example it would increase delete delay when hit with rate limit, but gradually try to decrease to find sweet spot where rate limit wasn't hit.

Now, the current version increases the delete delay but never tries to decrease it. Yesterday, I was testing with current version and it increased the delay way up to 6500+ ms, while I found that 2500ms worked just fine. So, it'd be nice if the current version could be made to find the right frequency of requests rather than staying way above the limit.