I still use a rig built 4 years ago. My mom uses one that's about the same, but before that, she owned a Dell tower that was 7 years old. Most of my friends own PCs that are 2-5 years old, but none of them would ever say that they use the web less. Besides Facebook (which is being shunned lately by folks I know) and Twitter, the web is quite vast and email, games, docs and music aren't the only things to be created or consumed.
Now I've had to replace my phone quite a lot more and I got a new tablet recently. These things will add considerable weight just by the rapid obsolescence and frequency of upgrades. The same applies to laptops (though I've used my old Inspiron 8200 with XP recently).
PCs enjoy a different domain in that regard.
So casual users of the internet/computers are going to start switching to other mediums to be casual on? That's fine.
So many people only use computers to check email/write small word documents/do other small-scale things. Those of us that use it for more, will stay on the internet, until something better that allows as much connectivity comes along (which it probably won't, but who knows) -- That means the internet will just be full of a different crowd, which is fine with me.
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