Time limits for unfocused discourse threads?

This post actually ended up being a good example.

  1. The original topic is thread time limits.
  2. The discussion prompted me to think about alternative methods to discourage mega-threads.
  3. I replied with one such idea (that would not have occurred to me without participating in this thread).
  4. We are now on a tangent about how a similar existing feature works.

Was this an okay reply in this thread or should it have been a new linked thread?