My iPad mini three, about 4 years old, is plugged into the mains whenever it is at home, I do not practice safe-battery processes. No issues at all with keeping a full charge, and have only once had the 10% warning, after 8 hours or so of surfing, mailing and reading.
Apple squeezes an incredible amount of stuff into a mini. Their priority is to make it as small as possible, not to facilitate battery, and other bit, replacement. Given the choice I'd go for smaller ...
Lots of third parties will replace your battery, if and when needed, for less than Apple. But Apple guarantees their results.
Last edited by ExXB; 14th Jul 2017 at 11:28.