Is there an off/disable control anywhere? I realize that the INFO button toggles it off, but it comes right back on as soon as you tap the shutter, and that it a problem in low light situations where the LCD keeps blasting me in the eye.
So, the answer to this is "no", there isn't. You can disable it in some circumstances, but as you've seen, it will keep coming back on. The user interface of many entry-level DSLRs is designed around the rear LCD screen, and these cameras also generally don't offer a huge amount of customization. This is also the case on the D3100, which is roughly a successor to the D40, and the slightly-higher D5100 model.
The D7000, though, has a small LCD status display on the top of the camera as well (as do mid-range cameras from other companies). Since that provides alternate access to key information, the software isn't as over-excited about turning on the rear LCD as it is on the lower models.
You can try covering the panel with Rubylith, astronomers use this a lot to dim bright display. It has a dark red tint to it so you'll still be able to see the display but it should seriously cut down on the eye glare and even retain some of your night vision. (Just some, it isn't perfect.) If the display has a dimmer on it, if you combine that with Rubylith you should have undamaged night vision.
I use this on my Palm Pilot which ran some excellent astronomy software and preserved my night vision perfectly.
This may not get you all the way, but you can turn off image review.
According to http://www.kenrockwell.com/nikon/d40/users-guide/menus-custom.htm, you can do this by going into the menus:
- Custom (pencil icon)
- 07 Image Review
Set this to Off.
To see this, you may need to set Full Menus in the Setup Menu (wrench icon) and be shooting in P, S, A, or M mode.
I'm afraid I've got to agree with the others - it's not possible completely. I'm also a D40 shooter and it's annoying late in the evening or at night. While all I need is visible in the viewfinder, the display flashes to the eye from below...
I tried to velcro a black rectangle over it. (First a piece of an old 8" floppy and then a thick paper covered by a black tape.) But it was pain although the velcro was undone pretty quickly - and got lost too :-) I thought I shouldn't need to get to the menu so often but at last I did need it.
You can also upgrade your camera to some else with swivel display and rotate it to make it face the body. Also, other cameras have bigger or brighter viewfinder better for shooting in the dark. And maybe a camera with the backlit upper display to be able to leave the LED flashlight at home :-)