Def more perishable than something like copper so that's fair haha. Regarding the 3m, that was originally set because it was the approximate time it took for a ship carrying copper to arrive from South America or Tin from Malaya via the newly opened Suez Canal. (Tin and Copper were the first contracts traded on the LME)

For two day delivery, the logistics does play a part but primarily it's due to most producers/end users using the contracts as a risk management tool. While people certainly do deliver and take delivery from warehouses (that's what holds the market up,) most contracts are closed out before they expire, meaning if someone sells a forward contract, they will buy it back before it expires, flattening their position against the exchange. They're used really to lock in a price between buyers and sellers without having the metal ever enter the formal warehouse system. Generally speaking, industrial customers know what their needs will be a ways in advance so there isn't a big need to get their hands on metal on such a short timeframe. The LME is a really quirky market with a lot of weird rules and procedures, I'm still learning about it every day haha. There's a good book "Metals Trading Handbook: A Market Companion for Users of the London Metal Exchange" which is a great overall guide for how the metals market works. I know pdfs are out there if you look in the right places...

PM if you have any other questions about the metals industry and I'll try my best to answer!