My K100d And K100d super use aa's and I've been lucky and haven't had this issue even though I've heard of it. The AA Lithium non rechargable batteries always gave me fantastic battery life and we're my backup batteries. If those are failing you I suspect it is a more serious problem than setting your battery type. I suspect you have some low level drain pulling down the batteries. 30-40 shots from enloops sounds bad - is that the same if you try a fresh never used set?
You might consider buying a newer body and making a battery adapter to use D cells or C cells on a wire. I had an old hp calculator that had a bad rechargable battery - it was from the late 70's and parts were hard to find. I made a d cell pack and suddenly it was able to run for days. In your case I might add an inline disconnect switch to avoid any residual drain condition between uses.
Last edited by UncleVanya; 08-04-2020 at 06:39 AM.