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Microsoft tries to convince Windows 10 users to buy a new PC with full-screen prompts
(www.theverge.com)
This is a most excellent place for technology news and articles.
If your Air hadn't reached it yet, eventually it'll reach EOS and you'll stop receiving software/OS updates from Apple. While this won't force you to upgrade hardware, it does add significant risk to your online time, since vulnerabilities will go unpatched. But, again, an important difference, which you shrewdly point out, you're not forced or coerced to upgrade.
Edit: autocorrect