It may be good idea to walk on "Overland Track" in different seasons.
As I knew one couple of Victoria walked multi-days Overland Track several times in recent years. The Overland Track for them looks like "Six-Foot-Track" of Blue Mountains or "Great North Walk" from Sydney to NewCastle for Sydneysiders.
My personal experience is that Ovelrand Track better than the finest track: Milford of New Zealand.
There are no any leeches or snakes or other dangerous insects except Sand flies in the tracks of New Zealand.
We are in AUS already, so we do not need waterproof cover carrying passport, instead, we could carry 2x6 bottle of Germany beers, 1 or 2 bottle of chinese white wine(s), have a show every night, and more and more.