Could you find the instruction manual for your washer and driver? For your furnace? How about that power sprayer?
As my wife and I clean out with the eventual goal of downsizing to a smaller place, I've found several big file folders with manuals for everything from a crockpot to a power sprayer. In that time, we've had many different coffee makers, as well as telephones.
We will occasionally wonder about when we bought a certain item and we guess. I bet we've missed it by more than a year or two on several occasions.
This week we bought a new replacement over-the-range microwave. This time I've put all the pertinent information on the manual. I've stapled all the appropriate receipts and submitted online my registration for this. No guessing anymore.