Exactly macaroona's point. If she goes to retire and her pension is worth zero because some radical muslim just dropped a nuke on Wallstreet, all this "put your money in the market for longterm growth" becomes a lot of hooey. I haven't seen anyone suggest that 10% of your assets should be in hard currency, like gold and silver, and in your safe, just in case of the above scenario.
Yes, and if some radical muslim dropped a nuke on Wallstreet, then the value of your pension is probably the least of your worries.
Gold and silver are not hard currency, they are commodities. And, in the case of the above scenario, you would probably be much better off with several guns and LOTS of ammo rather than gold and silver stuffed in your safe.