I'm just wondering what the max recommended speed is for leaving it in 4x4 high? I usually don't take mine over 60 km/h and was just wondering if it even matters. Will it hurt it if I go over 80 in 4x4 high for expended periods of time?

[2015 Z Force 800 53/Trail EPS]

It is never recommended in any 4wd vehicle, UTV or truck (does not pertain to all-wheel drive) to run in 4wd when not necessary, at excessive speeds.. or on hard surfaces. With these, even though all is still spinning while moving in or out of 4wd and the only difference is the axles are coupled to the carrier, I would avoid speeds over say.. 30mph in 4wd just because of stresses on components...replacement costs are over $900 usd after all....and I've seen a few broken cases. In 4wd with the diff-loc on there is an RPM limiter for safety. Whenever that comes in to play might be a good reference point to be out of 4wd too. Just thinking out loud. 

I agree 100% with NMKawierider. 

I say that it depends on the surface you drive on. If it's a loose surface or low friction for some reason I think it's fine to drive fast in 4wd but I woldn't do it on like a asphalt road.

Use as needed. 4wd is to get you out of a bad spot not in one. Jmo.

I agree 100% with NMKawierider.

And why burn more fuel and place extra wear on components unnecessarily? If conditions permit you to drive 50-60+ kph, you certainly don't need 4X4.