@onehillsheep this "it's been going from 100-10% within just 6 or so hours" will be a battery issue, not a charging port etc. Change your settings to more of a battery saving setting. Check the [https://www.samsung.com/my/support/mobile-devices/tips-to-extend-improve-samsung-galaxy-battery-life/|Samsung site] for the settings to improve battery life.
I agree, keep using it until it just won't charge at all anymore.