Here is more precise info
- we have developed Excel add-in using latest approach of (HTML + JS)
- using centralized deploying using office admin portal i.e settings ->Integrated apps -> upload custom app
- whenever we have roll out new version we increment version number and update manifest file using Action -> Update Add-in which works fine as per documentation
Here is quick snap of what i wrote above

The issue is that it takes hours (20+ hours) to trigger update on end user. I was expecting that whenever excel is restarted (with in few minutes) a user will get dialog of new version available but it is not the case here.
here is an article i found which says
"It can take up to 24 hours for a new add-in deployment to show up for all users. It can take up to 72 hours for add-in updates, changes from turn on or turn off to reflect for users"
Centralized Deployment FAQ | Microsoft Docs
i expect there would be setting or policy edit option in office 365 admin portal to change the default behavior. ideally, It should notify to end user right away whenever there is new version update available