IMO dirt can be discarded, but sandstone and cobble probably should not. Sandstone is not nearly as common or readily available as dirt, and cobble can be smelted into stone and crafted into stone bricks. You could make a largish separate room with 10-20 chests just for cobble, to keep it out of the way.
I've considered for a while making a big room inside that mountain where surplus goods can be stored and when a chest runs low they can refill said chest.
I'll work on it today. UPDATE: It's finished, you can find it below the storage lockers through a trapdoor. A sign there mentions it as the STORAGE RESERVE.
But, why cobble? It's infinite. Anyone can make or otherwise google on how to make a cobble generator, not to mention mining quickly fills a whole inventory with cobble. It's a bit of an inconvenience to grind it, but 10-20 chests might be a bit overkill? If huge projects on that scale are started creative often comes to look around the corner anyway, unless it's not a community-based project.
A real handy gimmick will be enchanted picks in 1.9/2.0. Instead of giving cobble, a pickaxe of silk touch will give you a block of stone when mining. Very useful.
As for dirt, it's handy to have one double-chest of dirt, for when you are building something and want to make nice flowing hills with no gaps in it, or to make a little garden or such. Once the chest is full discarding remaining dirt is a good idea, it's not widely used. Sandstone probably won't fill a double-chest anyway given how you don't run into it too often. A double-chest holds (27*2)*64 blocks of sandstone, I doubt it'll ever filled up.
But, I'll set up the reserve, it can come in handy and it gets rid of those ugly chests in the floor in the storehouse.[/quote]
