No, new entries don’t break the historical tag. When the system queries, it looks at all ids for a given tag path, and pulls all of the data together. In 7.3, new “created” and “retired” columns were added to make this more efficient, so that the system doesn’t need to look for data for ids where there definitely wouldn’t be any.
Better maintenance of this table is a big outstanding feature request. When you rename tags, or move them, unfortunately the system cannot track that and update the table. You end up with additional entries with different tag paths, which are basically like new tags.
If you rename or move a tag, the easiest thing to do is to change the tagpath column of the old tag to be correct. If using 7.3, you should set the “retired” column equal to the “created” column of the new entry. When you query, the system will read the data for all of the appropriate ids.