I used to live in LA and stored the albums in a heavy safe with double doors and nothing but coins in the safe. In 2010 the coins were put in a cabinet safe and moved to the midwest. In that larger safe there is only old newspapers and the coin albums.
I have never heard of nickels going gold
One of the problems people have using a safe is they don't realize that every time you open it, you allow air to flow in and then when closed, this new, sometimes heavy with moisture air, stays in with your coins. The amount of doors means nothing if you have moisture locked in now. And in the MidWest, the humidty is horrific and again, opening that safe allows moist air to flow in. In some areas of the MidWest, the air is a slight bit contaminated with Sulfur Oxides due to all the steel mills that used to be in some areas. Also, many of the older power stations, such as Fisk, burned Sulfur Rich coal making the surrounding areas full of Sulfur Oxides. So now every time you open your safe, you allow almost all sorts of contaminates to flow in and stay in.
As long as you continue to use a safe, I suggest you place all Albums in Zip Lock Plastic Bags. Push out as much air as possible and seal.
Or stop using a safe.
Or send all your coins to me and let me worry about toning.