Yes, I usually keep it mid way up but on certain things like cut scenes, areas of the game I know have interesting 3D effects I put it up full blast.

When battery life is a concern or I am playing a VC/DSiWare, I slide off though.

Not at all.

you need to free your mind in order to play with 3D on always. Like me.

I say this because it is not about your eyes, but your mind is fighting your eyes about what you see. 

I play with it 100% on, at least so far.
I also take boobie pics in 3d.

it's on all the time. when I first time played wiiu offscreen, I thought something is not right. until I noticed that the 3d is missing. I got a 5800mAh battery, I rarely need to charge.

Always, yes.

Yeah.

Well, sometimes. I guess it depends on the game. For something like Fire emblem or SMT IV I usually will just because the 3d effect isn't really going to hurt my ability to play the game. I turn it off for stuff like OoT though because it just adds an unnecessary challenge.

Haven't really used it sense I played Super Mario 3D Land, its the best looking game in 3D to date IMO.

Out of interest how is your eyesight normally? is there a difference in your vision between both eyes, say if you cover one then the other can you still see just the same? Reason I ask this is because I have a slight scar in center of my right eye which meant that the effect of the older 3ds's 3d was really hampered but at the same stage on the XL the scar covers less of the middle of the screen so I can properly enjoy the 3d on that bigger screen.

Btw are you aware that you can fully disable the 3ds's 3d in the parential menu? so that when you launch games it's 100% 2d and doesn't waste power on the feature if you wanna leave it off completely.

I may actually fully use the 3D a lot more in Pokemon X/Y during battles. It's not hetic or fast paced input-wise, and all the actions are selected on the bottom screen, so a sudden bluring of the top screen wont really affect anything.