There are more than just one available setting, so the "365 days" might not be enough (it may get to the size limit, just as an example). You might want to check the specific settings for shields ("expert settings" for each shield) and in each particular scan.
The path is in ProgramData -> Avast Software (or Alwil software) -> Avast (or Avast 5) -> log -> there should be several logs.
I am writing the "path" from memory so there might be a little difference (it also depends on OS and Avast version), but that should be enough for you to find the exact path in your particular case.