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  • Moses Chung thinks this is interesting:

There is no limitation to how many sublevels OUs can have. Having more sublevels helps categorize objects in the granular level, but at the same time, it will add to the complexity of managing the structure. This is especially effective in Group Policy management. Therefore, try to keep it under three sublevels.

From

Cover of Mastering Active Directory

Note

I read somewhere that the OU limitation was 10 sublevels down. I wonder if this was removed with 2016 Active Directory?