Battery

Apple considers the batteries to no longer be fit for purpose once they drop below 80%. You will also notice that the phone slows down and drains more quickly. Unless you are planning to purchase a new phone in the next few months, I would recommend getting the battery replaced. It will feel as if you have a new phone.

Genius Bar Reservation and Apple Support Options - Apple

I believe Apple recommends replacing a battery once below 80 percent health. However, that may still depend on your use and whether you feel you need a replacement at this time. If it continues to hold charge for your needs, you can probably wait.