OK, good catch, it is a bug. I had not recognized Long.MAX_VALUE in your query. The LuceneIndex class converts the neq to a range query and adds + 1 to the requested value without any check. The writer must have thought nobody would notice. It works for:
g.V().has("age", P.neq(9223372036854775806L))
If you want, you can report it as an issue.
Best wishes, Marc
