I like my iPad mini. Wish it had an SD slot, but that's about the only thing I find lacking. As far as batteries, I would be surprised if you couldn't change it, you can replace the iPod batteries. Might not want to, due to the dissassembly required; might not want to pay the bucks to have someone else do it; but, IMO, after 3-4 years I'll be ready for an upgrade.
I have Nextbook, 7 I think? which isn't bad. SD slot but no Bluetooth, no camera. Worked ok, but my wife knew I wanted the camera, hence the upgrade. The Nextbook gets used to hold music at work.