I’ve heard that Lithium batteries are most stable at 50% charge and anything above or below that causes their capacity to degrade.

If I know I’m going to be on my phone for a few hours and a couple of full charge cycles, is it better to disconnect my charger once the battery reaches 80-100% and reconnect it at 20%, repeating this several times?

Or is it better to leave it sat at 100% for several hours?

Which causes the least degradation to the battery, if any?

I always use a 2.4A battery pack or a 2.1A wall charger to charge it, if that makes any difference.

I have my iPhone set to vibrate and show a notification when the battery is full to remind me to disconnect the charger (within Shortcuts > Automation).