my worry is moisture/water build up. the oil never gets hot enough to dry out.
I believe there is a fair amount of blowby and acid production into the oil, and I've never liked acid and bearings living together.
A possible solution to that issue would be to install a fine mesh at the bottom of the sump, covering (say) the bottom 1/2". Any water (which is how the acids get around, since you don't get acidic oil), would tend to settle down below the mesh. The purpose of the mesh is to prevent it getting sploshed up into th engine when it's running. (By the way... I have no idea if that would work, you might need a solid screen, with only a tiny hole to allow moisture in the oil to fall through). Anyway... assuming you can keep a small moisture-trap space below the sump from being unduly disturbed during running, this could be periodically drained manually. It wouldn't take long before you got an idea of how much water was coming out of the engine, and thus the drain intervals. And it keeps the acid out of the way...
Just thinking out loud, really... feel free to poke holes in the above.