You're just trying to justify your new toy.
Tablets are not going to be obsolete any time soon. Will a lot of people not buy them in the coming years? Yes, that is already beginning to happen. When you have a phone with a 5-inch+ screen, there is no need for a tablet, except for special case use. Plus, when you buy the first one, it is hard to justify an upgrade when it works perfectly okay still.
The standby is impressive, but then why exactly did you pay all that money to have a smartphone, if you're going to just use it like that?