30 seconds is much to short to be of use. Can it be altered?
Sadly not, unless Brymen were to release a firmware update, along with instructions on how to flash it. Unlikely.
Edit: That said, it should be possible to power the backlight LEDs separately - perhaps wiring them up so that they're on whenever the meter is on. This would of course shorten battery life dramatically, but since I use rechargeable batteries and always have charged spares to hand this might not be too bad. Assuming a dozen or so mA draw, battery life should still be many hours. Alternatively, find a way to mount a physical switch for turning the backlight on/off.
I really cannot understand what the purpose of "auto off" on the backlight is; if I press the button to turn it on, that means I need the display to be lit - and I am perfectly capable of pressing it again when it is no longer needed.
Edit 2: In fact, this is one of the main reasons I'm thinking of getting the new EEVBlog 121GW meter...