I'm not quite battery watching anymore but I have changed the way I charge my phone. I used to 100% it every night without fail (came from an XS). But now because of the unbelievable battery on the 13 PM and wanting to preserve the battery health I'll charge to around 80% in the evening and that's normally more than enough to get me through the next 24 hours.
Of course, on days where I know I won't be near a charger all day (that anxiety still exists) I'll charge to 100% before heading out in the morning
This is exactly what Ive been doing with the 13 as well!
It also has its own cellular service through EE (I think its literally only an extra £5 a month) and it comes in handy quite often when I want to pop out and don't want to grab my phone, which means I am still contactable in case of an emergency.
Yeh its £5 on O2 as well. I think I may add it back on. It does come in very handy for the odd occasion when popping out.
I also tend to leave my phone in my office at work, and when I wonder around the building I don't always grab it and take it with me - the watch comes in handy there too I guess (I dont use the work wifi just so I can use some of my data lol)