Yes, it's very common for the active fermentation to slow in a short time. The yeast has consumed most of the easy sugar and has created a bunch of new compounds in the process, mostly carbon dioxide and alcohol but lots of other compounds too. Once it has eaten the sugars, it begins breaking down some of the other compounds that we think of as bad tasting. Letting the yeast work longer allows it to complete the clean up.
the knowledge I have leeched
I thought the term for that was Hoovered, like in Hoover vacuum cleaner. I have hoovered up a lot here too.