Use Apple Watch only for running - what to do when not in use?

Since the watch is "not in use" for most of the day, just turn it off before placing it in the drawer. After 2 days, there will only be a minimal loss of power. Charging will not be necessary for many days using that procedure.

Additional battery advice is provide in Apple Watch Battery and Performance, and Batteries - Maximizing Performance.

I would enable "Optimized Charging", then put it on the charger when not in use. It will stop charging when it reaches its charging goal. And it will learn your charging habits, and most of the time, it will just sit at 80% charged, which should be more than enough for a run.

I actually ware my Apple Watch everyday all day long, and charge it at night. I is 5 years old and has 90% battery life.

As for my Macbook Pro, I have never really had any issues with my personal Macs. My company Mac was on a charger 24/7 BEFORE Apple implemented optimized charging, and it needed a battery replacement. And the same happened to a lot of other company employees, again BEFORE optimized charging.

Since optimized charging far fewer company employees, based on company Slack channel messages, have needed batteries replaced.

For my part, after the battery replacement, again before optimized charging, I installed AlDenta and have limited my company Mac's charge to 80%. But again according to Slack messages, most users that keep their Mac on the charger 24/7 find that the battery stays at 80%.

macOS optimized charging attempts to learn your on power/off power habits, and only take your Mac to 100% just before it expects you to remove your Mac from power. If you are not consistent in your power usage, it becomes difficult to guess when the Mac needs to be at 100%.

Now my iPhone is always on the charger overnight, and in the morning it tells me that it will be fully charged in and around the time I normally take the iPhone off the charger. Until then, it is not at 100%.

So I've seen optimized charging work when I am consistent.

But this is about your Apple Watch. You are. not going to leave it on the charger for the rest of your life. You are going to take it off ever few days, or maybe once a day, and that will allow the Apple Watch to discharge the battery on a regular basis.

The WORSE thing you can do is allow the battery to go to zero repeatedly, as that is an even faster way to destroy a Li-Ion battery.