I charge weekly, after one week the battery is usually at ~50% with my usual usage. Obviously with GPS on the battery empties much faster, without any notifications etc the battery can hold multiple weeks.
But I'm not sure it's what OP is after. The requirements are:
> Phone notifications (so I don’t miss calls/ texts)
> Step counting
> A long battery life
Bangle.js doesn't connect to your phone at all, so you won't get any phone notifications. I don't personally use step counting, but when I have tried it I found it didn't work very well. Maybe that's just me.
The battery life depends a lot on what you're doing. In particular, clock faces that show seconds (i.e. have to wake up the CPU every second) drain the battery faster than clock faces that only go down to minutes. It still easily lasts longer than a day, which is good enough for me. I just charge mine overnight.
Apparently you can actually connect it to phone notifications using gadgetbridge[0] but I didn't have much success when I tried it. The BLE was a little flaky at the best of times (pairing to a PC for programming failed more often than I'd like).
idk if Bangle1 strap is different but (don't remember exact measurement) you can put any standard watch strap with a normal strap pin on it. I replaced the broken stock strap with a nylon one off the net and it's great.
[0] https://f-droid.org/en/packages/com.espruino.gadgetbridge.ba...
I love my Bangle.js 2, and have written my own watch face for it.