I've been using a Valentine 1 (and, previously, other brands of detectors) for many years.
One of the biggest surprises you get when you first start using a radar detector is how seldom you actually drive through a radar trap. You can observe for yourself how often, or how seldom, you see a patrol car. If he's got someone pulled over, his radar is probably off. If he's on the move, his radar may be turned off, too. Keep track of how many patrol cars have the driver actually watching traffic and ready to shoot the radar gun, and you'll find it's nowhere near as many as you think.
My V1 has never alerted for SUV brake lights or for electronic toll collection system sensors (which are widely used here). Ever. Like all radar detectors, it does alert occasionally for automatic door openers at supermarkets and other electronic devices, perhaps because I use it in the less-discriminating but more-sensitive "all bogies" (A) mode.
I agree with BB's assessment. Your unit is probably working just fine.