Not sure which agency you're with but with CCAP, around 7/8 months in they send a note to both HF and AP to talk about extension. I use that as a jumping off point to offer extension or not. If not, then I say something like "I just received an email from CC about extending for the next year, did you? [after AP's response]. We've thought about this a lot, and we've decided to look for an OOC AP for the next year. We've had a great year with you so far, but we [at this point...what's the truth, say that:]
- we like to host APs for only one year, after our last AP extended we felt like it was too long for both of us, and I don't want our relationship to go south
-or-
- we think you'd do better with a different family [more/less/younger/older kids, city/suburbs/driving/no-driving]