I cast using 6-cavity molds for .38 spl and .45 acp, using an RCBS 20 lb. bottom pour furnace. The problem was having to frequently stop to wait for the melt to come up to temperature after adding more scrap, with a lot of down time.
I had an old 20 lb. furnace for ladle casting sitting unused. Today, I plugged both furnaces in and used the old one to melt and heat to full temperature while casting with the bottom pour. Then when the metal level got low, ladled in premelted lead and continued casting. New scrap was heating up while casting. Can't believe how much faster it is. Figuring the hours saved, having a second pot to premelt is well worth the money.