Just bought a new Iiyama 19" monitor and am wondering best settings for a long life. I've currently got the computer to power down the monitor after 30mins of no use - to save juice and the monitor tube. Is this a good idea? Is it best to just leave the monitor on all the time? Will the turning on and off cause more problems than just leaving it on? Any advice appreciated ...

Leaving your monitor on all the time is not a good thing to do at all. Mostly because of the needless waste of electricity. Go ahead and set it to shut off after a certain time; that is what that feature is for. Actually I don't even use the automatic shut off feature; I just turn mine off anytime I go away from the computer.

turning your monitor on and off is very bad for your monitor. The general rule is that if you'll be back within the hour, to just use a screensaver (i use a blank screen as a screen saver). If you won't be back for more than an hour, have the monitor power down. Usually if I'm not back within 20 minutes, I know I'll be gone for at least the next hour...so that's when I've set my auto power off. So just try to set it so that it can sort of predict whether you'll be back or not.