I can feel another experimiment coming on!

Yep, never could understand how you could put a date stamp on a spud!  The majority of my family wouldn't buy reduced food items and Helen wouldn't buy them either. 

I do agree about using your common sense, using smell and sight as much as sell by date to buy food, just like our forebears. Sometimes stuff seems to be reduced when it's nearing its sell by date,rather than on the date, but I have bought stuff before which still had many days left.