Old classic doubles i doubt will lose value because you cant shoot them. From the auctions ive seen on the internet the guns that have the highest asking prices are the ones that are "unfired". Millions of collectibles are useless but not worthless. If your looking at your doubles as pure investments with the sole intent of selling and making money then you shouldnt be shooting them for risk of depreciating their value.
Like Mr. Brown said steel today is alot different from the first steel loads and i would think better then the first steel. If you havent shot new steel recently, maybe its not as bad as you say it is.
When was the last time you took a brand new to you gun out hunting and hit everything you shot at in the first ten rounds. A double is a very differnt shooting platform then the pump thats fitted to me.
Im trying out hevi shot in my gun, the first trial was terrible. Probably similar to your first try at steel. Im going to keep testing it out and see how it goes. If i dont like it i wont shoot it. Maybe in the next ten years there will be steel or something else that is safe to use in doubles for non hunting purposes, all im saying is it wouldnt hurt the ammo companies to start shifting from production of inbetween varmint and rifle calibers to efficient and cost effective production of non tox. You say there are no metals equal to lead, who says it has to be metal.
Im done with this.