Having recently blogged about promotions you can't win, my in-store lie-detector this week randomly turned its beady beam onto long-life light bulbs - or, as they should more accurately be called, not-really-very-long-life light bulbs. I've been buying these things for some time now, in the genuine belief that when a big red flash on the pack states "10 years", it means the light bulb lasts lit for 10 years. After all, isn't this the great age of "it does what it says on the tin"? Apparently not. ................................................................................................................................................................................................ If I may enlighten you - should you labour under the same misapprehension - when it says "10 years" it really means 1.14 years. (That's the equivalent in years to the 10,000 hours the microscopic print on the back of the pack - Philips in this case - reveals to be the true life of the bulb.) How do they do that, then? ................................................................................................................................................................................................ Having had a deckers at the Osram website, it appears that they're all up to the same trick. A so-called "15 year" Osram bulb will last for 15,000 hours (or 1.71 years, to save you doing the mental arithmetic). Here the small print reveals how the optical illusion is achieved: "15 years... 15,000 hours... at 2.7 hrs daily use." 2.7 HOURS DAILY USE? What planet are they on?! The dark side of the moon, it can only be. And certainly not one with kids who - as you may know from bitter bill-paying experience - are genetically programmed to leave lights switched on. I repeat - 2.7 hours! - this is the kind of calculation that could only have any relevance in Reykjavik in high summer. ................................................................................................................................................................................................ It's the garage forecourt equivalent of - instead of the pumps being marked in litres - petrol being sold in "miles". Imagine - you pay your £100, the pump tells you you've got "917 miles". Whacko you think. Then when you run out on the hard-shoulder of the M6, the AA man points out the pump calculations are based on the Prius, and you're driving an 8-cylinder 4.2 litre Chelsea farmer job. What did you expect? ................................................................................................................................................................................................ What you expected, of course, was the seller of the goods to tell the truth. Trades Descriptions Act and all that. These light bulbs - I mean - it's not even as if it's a dodgy promotional offering that never saw the light of ISP. No, it's the standard packaging that's getting away with one almighty whopper. A new definition for the light year, I would observe.