I mean, to be the safest, you can print a copy of your bill and gather it with many other bills to be stored in a file cabinet. Maybe put the cabinet in a climate-controlled room... I don't think that's necessary.
One time I cannot find a receipt, or legally a proof of purchase, to receive warranty services. I went back to the vendor for this very purpose to ask a duplication of the receipt. Luckily, they were able to reproduce it.