In MS Edge Internet Explorer Compatibility Mode has a default 30 day period (30 days is number of days that a site remains on the local IE mode site list)

Question

If you want to extend the 30 days you can use this policy InternetExplorerIntegrationLocalSiteListExpirationDays (https://learn.microsoft.com/en-us/deployedge/microsoft-edge-policies#internetexplorerintegrationlocalsitelistexpirationdays)
to modify the days that a site remains on the local IE mode site list.

If you enable this policy, you must enter the number of days for which the sites are retained on the user's local site list in Microsoft Edge.

The value can be from 0 to 90 days.

How should a corporate IT team approach this for Windows 10 enterprise ?

90 days is an improvement but would be better to choose a longer period bearing in mind MS Edge will be supported for years to come is it possible.

Answer 1

In general it is recommended to not use the Internet Explorer mode and to consider redesign websites with modern website standards.
However, in case you have any specific requirement and need to extend this, I advise you to send a feedback using the feedback option in the Microsoft Edge and make sure specify like required maximum date and explain why you need this feature. Take a look at:
https://answers.microsoft.com/en-us/microsoftedge/forum/all/how-to-report-a-feedbackbug-to-microsoft-edges/20cc8eb5-11bb-43b6-95d1-e004d41ef876