Well, pickles lasting longer doesn't surprise me (clue in the word pickle and how it is made too!)I never take any notice of best before dates either. I usually only keep a couple of tins of each item in the cupboard (or four in the case of tinned tomatoes) and replace as and when they are used. I buy some packet foods in bulk, so in those cases the best before date is often long gone. So long as they are kept dry and in a steady temperature they are usually OK.
I recently finished a jar of home-made pickle that was four years old and there was absolutely nothing wrong with it - in fact a much, much younger jar of Branston (which had only been opened a couple of weeks and was still well in date) was thrown out because it had developed a bloom. I should really have taken it back but the cost of petrol to take it back was far more than the cost of the product. Commercially made jams don't seem to last long either.
Spices and herbs are usually fine if they have not been opened. They do lose a bit of flavour once opened, however, so in those cases I just bung a bit more in The large pack of chilli powder I bought some time back is still hot!
However, would you be so unconcerned say, if it were a tin of crabmeat that was 4 years old?
Commercially made jams tend to have less sugar now (which I welcome) and often say to refrigerate it once opened.