Eating batteries

My Stingray 5-H is eating batteries like crazy. I might play it for 8 hours spaced over a week and the preamp starts distorting and I know I need to replace the batteries. I unplug when not in use. I don’t understand why the drain happens so quickly.
It’s annoying and expensive!

Aside from taking the batteries out every time I stop, anyone know why it’s just running through them?

All settings at unity not messing with them and selector switch in the 1 position (parallel).