I think it’s important to measure both the FIRST response and the BEST response. For example, the first response is a sign of attentiveness, immediate feedback, and member engagement. If you can provide the first response within the average bounce rate of the site, then you should be able to retain the member longer. One obvious problem with the first response is that it might be a bad response. It could be a peer asking for more information (so the problem isn’t solved at all), an offtopic comment or feedback (irrelevant to the actual solution), or an attempt at a solution that’s incomplete or incorrect (doesn’t adequately solve). That leads to the BEST response, which will be the true measure of your community.