Proper Jungle Rotations?

Now, I'm not gonna claim to be a great jungler, so my advice on this may be somewhat unreliable, but if I see the other jungler spending a long time laning in any particular lane I see this as my opportunity to do whatever the hell I want.

If my teammate is struggling, in this situation, then I will attend the lane to stabilise the situation and then tell them to just hold lane as best they can while I go do other things (it's easier if I can speak to them to say this, but if not pinging your teams tower then calling 'defend X lane' then 'bye' on vgs usually suffices). Once I leave I'm free to do what I want (camps, ganks etc) without having to worry about the enemy jungler.
So now in this time I can do stuff to help the two other lanes while their jungler is only helping one. And think about it, if you get a good gank in this time it's going to help push a lane a lot more than the enemy jungler just laning.

Or sometimes the enemy jungler will leave the lane when they see me leaving, making it an even lane battle, for the lane they were in, again.

Of course there are some circumstances that will make me stay in the lane till the enemy leaves (for example the enemy jungler is helping push the lane because your tower is very close to being destroyed), but like people before me said, you get a feel for these things.