Keeping the level 20s and 40s both on cooldowon, seemingly like 85% of my responses are charity/tech, 15% are vacation, and the last time I got a tax was 6 days ago. 43k addresses (I spammed the farm button on day 1 :P)
Emforus' guide says
Response queue and awaiting response
If you get the "Awaiting response..." message at the bottom of the spamming page, it means your last wave placed responses on the "queue". This means that you'll get a predetermined amount of responses over an undetermined span of time until the queue is empty. Once the queue is empty, the Awaiting response message will disappear.
This is particularly useful for the more advanced scam categories: Scams like Job, Advance-fee and Tax may not place any responses on queue after sending out one or more spam waves of said categories. This is a good sign that you need to get more email addresses.
Maybe there's a threshold for them, like 50k for tax to start being common, or something?