My general and absolutely non-scientific observations are that many people will never stay until a park closes. And that doesn't really vary depending on the park closing time. So, if parks are closing earlier then many people are leaving the parks even earlier. Having spent a lot of time in the tourism industry and also restaurants fall and winter almost always mean earlier dinner times and earlier bar usage.
Sadly, if true, this probably points more towards starting the complete shut down rather than having much to do with lack of business. The 5-6 hour is a time that we would personally go to the TOTWL and have in the past.