auto power off timeout

[npelov]

I have few battery powered devices with automatic power off and few without. I lost quite a few batteries by forgetting the device powered on, but I also have troubles with devices that have automatic power off. For example MS 8220R multimeter times out after 10 minutes. That's too soon in my opinion. I think for a multimeter that does not take into account significant change in reading for it's auto-power off the minium is 20 minutes.
I have the same problem with backlight. Even my top of the line Brymen BM-869 multimeter has bad value for backlight timeout - about 15 seconds. If it had dedicated button for backlight it would be less annoying but every time I need to measure in the dark I have to press and hold "select" button and it is barely enough for one measurement. Sometimes you would sacrifice a battery for 1-2 hours work in the dark (or in my case I would have to charge the battery again).

So I thought I ask everyone: What is your best value for auto-power-off and backlight timeout functions of battery powered devices? Or if you could choose between 4 programmable values what would they be?

I know it depends on device functionality, but still if you had a chip that implements that functionality what would be the best timeout value(s) for it?