Iphone Battery health

Apple recommends changing the battery when the health is below 80 percent. There is no need to replace it now. I don't believe Apple or any authorized service provider will even replace a battery that is not below 80 percent.

For what it's worth, my battery health is at 75 percent and I have no plans to replace it yet

That is a very poor idea, when Lithium Polymer batteries drop below 80% battery health they begin to respond erratically and will eventually begin swelling to try to keep up with running your device. And it can swell and pop dramatically thus killing the device and in some cases presenting a fire risk.