Cellular watch battery

Well yes, the cellular chip consumes fair share of power. but then again, it is important to have Wifi always enabled and when you do that, the cellular is not used anyway. Then when Wifi is not available, you might indeed want to have cellular on. So perhaps not that much benefit in doing that manually after all. Unless you have some specific use case in mind.

Batteries - Maximizing Performance - Apple

Apple Watch is, for lack of a better term. parasitic, and will use the paired iPhone and its devices and its battery reserves whenever that paired iPhone is within range, and using Bluetooth for those communications.

The cellular radio within the Watch is powered up and fully active only when out of range of the paired iPhone.

You can tell that too, as the Watch lasts a whole lot fewer hours when on battery with cellular active. I don’t see Apple specs published for Watch SE, but Watch 6 lasts 18 hours within range or the paired iPhone, ~6 hours on LTE standby, and ~1.5 hours active LTE.

Now if you’re out of range of the paired Watch, and are not using cellular, sure, you can switch that off, or switch to airplane mode. That’ll lengthen run-time.

With Watch Series 5 and later, switching off the display (theater mode) can also substantially reduce power consumption, and can lengthen battery run-time. And not by a little bit.