I'm certainly no expert, but...
An excellent book on the subjest is WORLD CRUISING ROUTES by Jimmy Cornell and a quick downwind circumnavigation can be done in about 18 months if you are really hell-bent on doing so.
It'll be over before you know it, so be sure to take lots of pictures.
I've been trying to "connect the dots" since cutting my lines in Hawaii 12 years ago!
Been sailing west (mostly) and have only made it as far as the Caribbean.
Too many plesant distractions in places like Australia, Palau, the Philippines, Borneo, Malaysia, Thailand, Egypt, Turkey, Greece, Malta, Spain and the Caribbean keep hanging me up and slow forward progress.
Yet, somehow, I've logged 25,000 nautical miles & smiles along the way... while loving life to it's fullest and have been rewarded with a lovely wife, a bigger boat and a fine son while enjoying life "Out Here". The ultimate souveneirs of a great cruisnig adventure!
Why the rush?