There are advantages and disadvantages to each licensing type.
The main advantage of concurrent use (CU)-single point of managing licenses, 1 license can be use by multiple users (one at a time). Users can select/deselect core and extension licenses.
Disadvantage-once a license is consumed, no one can start the application without additional licenses. Must be on the same network as the license manager.
Main advantage of named user (NU)-user will always have a license assigned. User can use Pro on up to 3 machines at the same time. Only requires Internet access when using NU license through AGOL.
The main disadvantage of the named user licensing option is that the organization must have equal or more licenses than users assigned.
In your situation, I don't see much benefit to retaining a named user license. You have to maintain the license manager for concurrent use and the licensing portal for named user. It make sense to convert them all to concurrent use. From a user's perspective, there is no difference in functionality. The user can use the tool if licenses with wither concurrent or named user licenses.
