Without stripping the motor there are a couple of tricks to try before fitting any version of cut off valve to the oil supply side.
Preventing air entering the oiltank will slow the rate of draindown. So a good fitting and sealing tank cap is a must, along with some convenient way of blocking and opening the tank vent to atmosphere.
Another madcap scheme is to take off the sump drain plug and tank cap after every run and just let the whole lot settle into a nice clean catch tank. This will also carry down any contaminants which will settle out, but does not empty the oilank completely, only to the pipe exit level. Then for the next run, refill with fresh oil, and next time use the first oil again, leaving the muck to be cleared out and dumped. This way the oil gets used in a constant cycle and some contaminants are removed from the engine. But it's such bother, although in the short term it avoids any major mechanical work.
Oil in the tank reaches the pump by gravity, the pump itself runs in oil, and running completely dry is only possible if the tank is empty or the flow obstructed.
All schemes require a bit of memory or reminders, that's why doing the job properly lets you sleep easy.
Swarfy.