I've had my Series 4 since it first came out. I put it on the charger every night, and remove it in the morning. It is powered on all the time, unless I'm intentionally doing a power cycle to clear some glitch.
It is now 6pm and I've have had my Series 4 on my wrist since 9:30am this morning.
I have 73% charge left for the day. By the time I put my Series 4 back on the charger tonight, it will be down to maybe 50% plus or minus. Maybe higher today, as I did not do an hour of exercise tracking today.
The Ultra can go longer between charges, but that is mostly useful to people out hiking, or long distance runners (as tracking your exercise does draw more power checking GPS all the time, and running the heart sensor, etc...).
But it does not hurt the Apple Watch to charger it before it is low.
In fact Li-ion batteries Do Not like being drained to zero. That is one of the fastest ways to destroy a Li-ion battery.
If you are very vigilant about making sure you charge your Ultra before it gets too low, then fine, do not charge it every night. But I strongly suggest you put it on the charger when it drops below 50% (as in you look at it before going to bed, and it is less than 50%, you put it on the charger even if it was not when you would normally schedule a charge), unless you are truly on a multi-day hiking/camping trip.
When I say less than 50%, I just mean that if it is less than 50% at 9am, you plan on charging it when you go to bed that night. I do not mean rush to the charger at 9am. The Ultra should have more than enough power to last the day, but should be charged that night.
Personally, I am not that vigilant, and I prefer the habit of doing the same thing every night, so I would be putting the Apple Watch on the charger, as I do now, every night, unless I'm not in a position to do it (traveling, etc....)
