Samsonite did once offer lifetime guarentees - when they made luggage that was strong. I had been loyal to them for a long time, but my overnight wheely bag failed after 6 years hard use and the replacement lasted just past the one year guarentee. So I'm now buying cheap unbranded bags knowing that they will last about a year and cost about ten times less.
However, I was very impressed with Samsonite ten years ago when I bought a US$40 wheelie briefcase in a COSTCO in the USA many years ago. It had a 2 year worldwide guarentee and the handle broke just before the two years was up. I took it to the local dealer who said they would have to send it to Samsonite UK. I forgot about it until about a year later, when I called the dealer who mentioned they would chase it up. An hour later, I got a call from the managing director of Samsonite UK who said that the bag was a model made for the US market in Mexico and thay didn't stock the required parts, so they would replace it with an equivalent model - and what's more, the managing director would deliver it to my house that evening! It turned out that he lived four doors away from me and the bag he bought me retailed at 160GBP!
It's a shame they have gone down mass production low quality route. They used to make some good bags.