It was a common assumption of mine that the warranty period for a product started the day you bought it. I found out the hard way that that is a very poor assumption. It appears that it is based on the manufacture or ship date from the factory, not the delivery or purchase date to the user.
Cases in point:
1) I received some laptops with 3 year warrantie; when I called in for service, the first thing they did was check that it was within warranty. Well, I had received them in Aug or Sep 2006, and the first thing I was told was that the 90 day software warranty had already expired before I received the laptops, and the 3 year warranties would expire less than 2.5 years from the date of receipt.
2) I bought an external hard drive from the local electronics store on Aug 21, 2008, and within 2 months, it needed to be returned because of failure. Going to the web site to get an RMA, I was told that warranty expired on Jan , 2013, which is less than 4.5 years from the day I purchased it, when it was advertised with a 5 year warranty. While the process of getting a RMA is straightforward, trying to correct the warranty date is not so easy. In order to correct it, I registered the drive, providing the purchase date. However, the warranty information did not change. On calling technical support/customer support on the phone I was told that since they had no way of telling when the drive was sold, they used the ship date + 3 months as the expiry date of the device, and the way to make sure I got the full warranty was to send in a copy of the receipt so the records could be corrected. Remember when you go to a store and buy a unit that has been opened and returned at a discount, and they tell you the original manufacturer's warranty still holds? Think again: if it is a returned unit, it has originally sat on the shelves for a while, and then the consumer has bought it, tried to use it, was not satisfied and returned it, and it sat on the shelves some more. So your 5 year warranty product may actually have less than 4 years left on it, unless you set the record straight right away.
Given how small the receipts are, and when printed on thermal paper how quickly they vanish, if you need warranty service down the road, trying to make a copy of the original receipt at that time will certainly not help prove that the warranty should actually be longer.
Given all this, what should be done? It appears that the best thing is to check the warranty date of these long warranty date purchases right away on the manufacturers website, and send in a copy of the receipt to make sure that you get the warranty you think you paid for.