Front hubs

For economy, Hubs are best left unlocked however once a month or so, lock them in for a few k's to keep them lubricated.

My suggestion is to leave them unlocked all the time. Only need to lock them in when you're about to do some 4 wheel driving. It saves wear on front drive components.
I usually lock them say in a car park or at camp etc just before heading into any rough stuff etc.
However, I also believe in having them locked and using 4 wheel drive when driving on gravel roads at normal speeds too. (eg: going up the Birdsville Track @ 80kph or so). A lot of people will say this is stupid, but I like the sure-footed feeling it gives and it's also safer if you have to brake in an emergency on the gravel. The reason for that is that the front and rear drive shafts have to turn at the same speed. With the vehicle in 4 wheel drive mode (centre diff lock engaged in a full-time 4x4), if you have to hit the skids in a hurry, the front wheels will be less likely to lock up as the rears would have to do so too. In part-time 2 wheel drive this is not the case. It also gives you a better chance at "steering around" a potential catastrophe too.
Just my 2 bob's worth.

Good idea to lock them in occasionally to ensure the grease is evenly spread through your CV/DOJ's. Also allows you to hear any prob's with the front end before you hit the tracks.

I agree a lot with Gary above to make sure that grease is warmed up and distributed. I have had grease dry out in uni joints and the uni joints give up after you need them next resulting in new uni joints. Has resulted in huge extra costs on top of those of wear.....

I agree with Roachie in the way it is good to lock them in to give a run on some rougher road, just to make sure it all works ready for next time you want it to. I don't know about the surefootedness angle but it just helps the lubricatiion and readiness.

Agree with Roachie. For outback tracks etc if the surface is loose enough, 4wd certainly maintains stability and helps iron out the corrigations. If the surface is hardpacked then stay in 2wd.
Its like the other chesnut "when to engage low range".
When in the High Country I will regularly use low range (up to say 30KM) just for the addional control and engine breaking especially when exploring new ground.

Cheers
Bob L

I use 4WD when needed but give the hubs a run once a month on GQ (manual hubs)

Thanks everyone for the responses...The answers were basically as I had thought