So I want to buy a Note 3 or Note Air but it is my first android device so I have some questions that I still have after watching Mydeepguide reviews.

1. I know the OS isn't updated to newer Android versions but how is it support wise? Android 7, which released only a couple of years ago is not supported anymore. So, when Android 10 is not supported anymore in a couple of years, how does that affect the device? I want to use it for 5 years. This worries me the most, because I hear Android phones lessen very quickly in functionality.
2. I can't find much about the ereader/epub functionality. 50% of the device usage will be leisure epub reading, both DRM and DRM free. Is it suited for that? Is it much worse than a Kobo?
3. Besides annotating PDF's, I want to annotate or at least highlight epubs. I don't care about exportability. From what I read it is very difficult to annotate (drm free) epubs. Can it be done reliably with KOreader?
4. Also, I'm don't know if I want the Air or Note 3. I worry about the screen quality of the Air, does the glass really break quickly? Is the battery life of the Air much worse ? I want to charge my device about once a week. Also, I read that the Note 3 has less contrast which would cause some eye-strain… what are your experiences with this?

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Thanks in advance.