-PJ
The batteries are very expensive. You need to make sure that you charge them up to around 60% every few months. Better still charge them fully every few months then fly the drone around until the batteries are discharged to 50 or 60% then put it back in the closet.
There are 3rd party apps that add functionality to the mini 3 and mini 3 pro. The two that I use are called Litchi Pilot Beta and Drone Link. I would advise against purchasing Drone Link despite it's slicker looking web page and promotional materials on YouTube.
https://forum.flylitchi.com/t/open-beta-litchi-pilot/10621
https://support.dronelink.com/hc/en-us/articles/15304402363411-Mini-3-Mini-3-Pro-Support-Overview
Litchi Pilot Beta is currently free and has more of the features that I use. I actually spent $120 on the most advanced non-business version of Drone Link and have been thoroughly disappointed. It is a severely hobbled version of their business program.
Litchi does everything that has been disabled in the Drone Link Elite version that I purchased for free. Both can be used to pre-program waypoint missions which means the drone will fly around and take the pictures or video you want with almost no input while flying. The difference is that only the business version of Drone Link can use altitude information from Google Earth and other providers. That Drone Link nearly worthless if you are hoping to fly in areas that have hilly terrain.