I'm a brand new 'Jira service owner' and our service is provided by both Jira Cloud and Jira Data Center applications.
Our Data Center applications are Jira Software 9 and Jira Service Management 5
Given cloud products (not just Atlassian Cloud but Google, Microsoft, etc) are 'evergreen' and are 'always on the latest version, I'm tempted to do the same for our Data Center products i.e. to also keep them on the latest version.
(and to mitigate the risk that the Atlassian or the 3rd party app vendors breaks something for us, we protect ourselves with the usual 'Stage > test > Prod' due-diligence)
But as I said - I'm brand new, so I'm looking for some confirmation that "yeah that's a great idea, and we (wish we could) do that because..." or "no that's a terrible idea because..." - I'm kinda learning on the job here...