And when you're not, edit your post to say you're too busy and then re-edit it for when you are again
Something like this:
Hi! I'm available from Oct. 1 - Oct. 8 to be a last minute challenge buddy for poetry! Drop me a PM if you need some help. Be sure to get it to me before 8:00 pm, so I can get it back to you quickly.
And then if you can't, simply edit your post, or add a new one that says you're not available until further notice.
Awesome idea from the ladies in the other thread