I’ll add me tupnth worth here.
I have in a bait bucket 2 types of boilie. 1 lot is Nash instant action Candy nut crush, the other is a tiger and maple flavour from a brand I had never heard of. The Nash are 15mm and the others 18mm.
They must have been in the shed 2 months. The Nash have gone rock hard but the others still soft. Don’t know why.
I also have a bag of Nash monster crab in the cupboard unopened. Giving them a squeeze through the bag they are much softer than the open ones.
All above are shelf life bait.