I will hit my 82nd birthday in less than a month. I have LONG preferred multiple cavity moulds. I have iron, aluminum and brass from nearly all of the major players. Aluminum five or six cavity moulds are my favorites, in general. However, I have some DANDY four cavity iron and brass moulds that work really well. I have no problem with operating these, but my six cavity H&G #251 (.358 dbl ended W/C), while a wonderful mould, weighs nearly five pounds. That IS fatiguing for sure. So, I tend to pick my H&G four cavity iron for the .358 W/C #50BB instead.
I used to do marathon casting sessions, but now I limit myself to one pot (RCBS 22.0 lb. pot) and cast twenty pounds of bullets at a sitting (yeah, limited by age and personal condition). That is NOT a bad thing, tho'. I just cast more days in the week...
I have a dedicated casting area in my heated and cooled utility barn, so no serious time is involved in setting up. I just pre-heat my mould on the hotplate while my pot is heating. In thirty minutes I am ready to roll. By pre-heating, I get good bullets from the "git-go", so it is all pleasure. I can do a pot in an hour to an hour and a half (.45's run faster than .32's (:>)...
I competed with black powder cartridge rifles for fifteen years. I had a couple of custom four cavity moulds (aluminum) and had NO accuracy problems with the multiple cavities in spite of all the Naysayers...
These days, all I shoot are revolvers and pistols, but that is fun, too (:>)
FWIW
Dale53