E-Reader, I've put hours and hours into that thing and it's still going strong. Maybe I'll upgrade it at some point, but it's showing no signs of ageing yet. I love reading, but I don't have space for a huge library of books (believe me I wish I did).
Honestly outside of moving to a more open platform
Kindle -> Kobo -> eInk Android/iPad (whatever floats your boat)
There's no point in upgrading since these devices literally haven't been updated hardware wise since 2014. That said I have a Color eink device and for me it was worthe the move, but I wouldn't do it again.