The bottom suggestion is for an insulated Obsidian Furnace. Any Fuel put in an Obsidian Furnace burns twice as long as it would in a normal Furnace.
The top on is for a Nether Lava Bucket. Each stack of Netherrack added to the Lava Bucket increases one multiple of burning time (i.e. a Lava Bucket and 4 Stacks of Netherrack would burn 5 times as long as a Lava Bucket).
Well, then I'm making a suggestion that, at least in this case, Crafting will work that way. It works for Gunpowder in Fireworks.
A further clarification, those are one or more full stacks of Netherrack. So a Lava Bucket with 512 Netherrack would burn for 9000 seconds, or 5 hours in an insulated, Obsidian Furnace.
I don't see a point in having furnaces that smelt longer unless they can hold more items; a furnace that burns for 9000 seconds should be able to take in 900 items at once. That is to say, even now I see no point in using anything other than coal, plus I use more furnaces if I need to smelt a lot of items (e.g. 8 stacks of iron ore divided among 16 furnaces, so it only takes about 5 minutes to smelt) because I don't want to wait forever for it to finish; I also only use coal because it evenly divides into a stack of 64 (no need to unload/restock to avoid wasting fuel, or using hoppers, but wasting XP) and is extremely easy to obtain.
Also, you can already use hoppers with a normal furnace to make an hours-long smelter, able to smelt 1,728 items at a time with just regular chests.
A further clarification, those are one or more full stacks of Netherrack. So a Lava Bucket with 512 Netherrack would burn for 9000 seconds, or 5 hours in an insulated, Obsidian Furnace.
Also, you can already use hoppers with a normal furnace to make an hours-long smelter, able to smelt 1,728 items at a time with just regular chests.
TheMasterCaver's First World - possibly the most caved-out world in Minecraft history - includes world download.
TheMasterCaver's World - my own version of Minecraft largely based on my views of how the game should have evolved since 1.6.4.
Why do I still play in 1.6.4?
This was in response to the thread the quote was taken from and it was suggested I pull the idea out.
I think the insulated Obsidian Furnace is a great idea though.
In that case, the Obsidian Furnace could let the Burn Times for a Furnace be halved. Then to be doubled when you can get the improved version.
Agreed.
Making burning times longer just makes the game easier. I can't see a reason for needing longer burn times.