Hub Locks On or Off ..... all time

[the evil twin]

All the GUs I've come across must be different to all yours. My GU doesn't have an "unlock" position. The two positions on mine are "lock" and "auto". I leave mine in "auto" and when off road in 4WD it locks automatically (funny enough) whenever required.

Whatever, but I can't actually "unlock" mine.

Your correct about the GU's but he has a GQ, Cobber

Leaving the GQ manual front Hubs or GU aftermarket/mod'd Hubs locked is no biggee, just increases the fuel use a tad and also a taddy bit of extra wear on tyres.
Might get a bit of extra NVH at higher speeds on bitumen as well.

It is a very good idea to 'LOCK' the GU auto hubs if you are doing serious wheeling (as per the owners manual).
When left in 'AUTO' the Auto hubs can get damaged in certain 4WD situations if you don't which is why some (not all) people who don't understand them will bag them out.