kube-controller-manager has the following property
-deployment-controller-sync-period duration Default: 30s
Period for syncing the deployments.
What does this actually control and what does period for syncing the deployments mean?
Haha most curious thing. You'd expect it does something like controlling how often the controller checks whether the status of Deployment objects are compatible with spec or if there is a change needed.
However currently the controller-manager is notified on changes by the apiserver so it always inherently knows this information already.
There is Issue #71510 where someone points out that parameter seems to be unused. I've done my own search for the parameter and a related search for the variable. As far as I can tell all of these uses are for copying this value around, conversions, declarations, etc, and none of them actually use it for anything at all.
A good test would be setting it to a year and see what happens. I haven't done that though.