Guarantees - do they mean anything?

As I pushed my trolley out of the Hyperama today, my eye was caught by a poster advertising Bushbaby camping equipment. I have bought a number of items from their camping department, as I mostly pitch a tent for a Star Party. The advert said the tent was guaranteed for one year, and it got me thinking about guarantees and how they might apply to different items.
Assuming I use my tent for 8 days in a year, is the guarantee implying that I can expect 8 days' use without a seam failure before the guarantee expires, or can I camp for 365 days before a zip breaks? One would hope the latter, as sometimes a year goes by without me even attempting to pitch a tent - the snow factor must be taken into account! This would mean a lifetime guarantee, as I doubt whether I could camp enough over the rest of my life to make up a year. But in reality, the manufacturer will assume that a calendar year is all it needs to allow, and it's your problem if you didn't use your tent enough. It is effectively no guarantee at all.
A car manufacturer will give you three years on the assumption that you use it every day, so they obviously have great confidence in their product. It's good to know that it will be three years before something goes wrong with one of our major purchases, but Murphy's Law dictates that on the day after the three years is up, it will be a very important part that gives up the ghost and makes a huge dent in your wallet.
Similarly, a kettle has a year's guarantee and I use mine at least 10 times a day. But the cost of a kettle is pretty low and the manufacturer knows that we are more likely to send it to the dump than attempt a refund should the kettle fail to boil one morning.
Some things are so badly made that they don't work the first time you use it, and that is the time when you really will make use of the guarantee period. The secret with these (usually household) items is to check the box they come in. If it has been obviously opened and resealed, it is likely that you are getting an item that has already been returned by a previous purchaser or (horrors) it was used by the staff to see whether they would like to buy one themselves. Not unheard of.
Guarantees are just a thumb-suck number of days and don't relate to the amount of usage. It's meant to make you think the manufacturer cares. What do you think?