NoItemsDespawn
This only-one-command just makes items invulnerable, resistant to lava, fire and despawning after 5 minutes.
NOTE: You need Minecraft 1.9 for this one (I made it on snapshot 15w35e (check the blog for more information).
The command:
summon FallingSand ~ ~1 ~ {Block:redstone_block,Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:fill ~ ~ ~1 ~ ~-2 ~1 redstone_block},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:fill ~ ~2 ~ ~ ~-2 ~1 minecraft:air},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~ ~-3 ~3 redstone_block},Time:1,Riding:
{id:"FallingSand",Block:stone,Time:1,Riding:
{id:"FallingSand",Block:redstone_block,Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:fill ~ ~ ~1 ~ ~-2 ~1 redstone_block},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:fill ~ ~2 ~ ~ ~-2 ~1 minecraft:air},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~ ~-3 ~3 air},Time:1,Riding:
{id:"FallingSand",Block:stone,Time:1,Riding:
{id:"FallingSand",Block:redstone_block,Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:fill ~ ~ ~1 ~ ~-2 ~1 redstone_block},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:fill ~ ~2 ~ ~ ~-2 ~1 minecraft:air},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~ ~-3 ~3 redstone_block},Time:1,Riding:
{id:"FallingSand",Block:stone,Time:1,Riding:
{id:"FallingSand",Block:redstone_block,Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:fill ~ ~ ~1 ~ ~-4 ~1 redstone_block},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:fill ~ ~2 ~ ~ ~-4 ~1 minecraft:air},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:tellraw @p "NoItemsDespawn for Minecraft 1.9 vanilla."},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~ ~-3 ~3 minecraft:repeating_command_block 1 replace {Command:"entitydata @e[type=Item] {Age:0s,Health:2000s,Fire:-2000s}",id:"Control",powered:1b,TrackOutput:1b,CustomName:"@",SuccessCount:0,auto:0b,conditionMet:1b}},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:gamerule commandBlockOutput false},Time:1,Riding:
{id:"FallingSand",Block:stone,Time:1}}}}}}}}}}}}}}}}}}}}}}}
NOTE: You need Minecraft 1.9 for this one (I made it on snapshot 15w35e (check the blog for more information).
The command:
summon FallingSand ~ ~1 ~ {Block:redstone_block,Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:fill ~ ~ ~1 ~ ~-2 ~1 redstone_block},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:fill ~ ~2 ~ ~ ~-2 ~1 minecraft:air},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~ ~-3 ~3 redstone_block},Time:1,Riding:
{id:"FallingSand",Block:stone,Time:1,Riding:
{id:"FallingSand",Block:redstone_block,Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:fill ~ ~ ~1 ~ ~-2 ~1 redstone_block},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:fill ~ ~2 ~ ~ ~-2 ~1 minecraft:air},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~ ~-3 ~3 air},Time:1,Riding:
{id:"FallingSand",Block:stone,Time:1,Riding:
{id:"FallingSand",Block:redstone_block,Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:fill ~ ~ ~1 ~ ~-2 ~1 redstone_block},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:fill ~ ~2 ~ ~ ~-2 ~1 minecraft:air},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~ ~-3 ~3 redstone_block},Time:1,Riding:
{id:"FallingSand",Block:stone,Time:1,Riding:
{id:"FallingSand",Block:redstone_block,Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:fill ~ ~ ~1 ~ ~-4 ~1 redstone_block},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:fill ~ ~2 ~ ~ ~-4 ~1 minecraft:air},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:tellraw @p "NoItemsDespawn for Minecraft 1.9 vanilla."},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:setblock ~ ~-3 ~3 minecraft:repeating_command_block 1 replace {Command:"entitydata @e[type=Item] {Age:0s,Health:2000s,Fire:-2000s}",id:"Control",powered:1b,TrackOutput:1b,CustomName:"@",SuccessCount:0,auto:0b,conditionMet:1b}},Time:1,Riding:
{id:"FallingSand",Block:command_block,TileEntityData:{Command:gamerule commandBlockOutput false},Time:1,Riding:
{id:"FallingSand",Block:stone,Time:1}}}}}}}}}}}}}}}}}}}}}}}