Try to keep instantiated tag names short. Remember that not so long ago printers were limited to 80 characters across a page!
The limit on a page tag is 32 characters
For a 'RealTag' it is 128 characters
For a hierarchical tag it is 255 characters
For an External tag it is 50 characters
With 16ch tag names the Real Tag the limit is 5 levels. And the hierarchical limit is 15 levels.
(The InstanceID, which is the actual limit is 200, so the maximum number of levels is 40 or so. The RealTag tagging will fail first, so you will need to reduce the levels if you use long very long tags)
For objects that are not instantiated (for example notes) there is no reason to limit the tag length below this number. For Instantiated objects the shorter the tag name in the object and it's parents the shorter it's Unique Instance tag will be.