sauce sachets?

[cherrybomb]

My daughter likes the packs of snacks with crackers or pitta's, with cheese and ham/chicken that you build yourself, but she never uses the sauce sachets that sometimes come with them. I often think that they would be handy to keep but does anyone know how long they would last for?
Thanks in advance.

[fine,thanks]

these snacks are very high in salt and fats.