I have three Extremes in one home, and a Time Capsule in another. Until the day arrives that they either all depart, or new technology just simply makes them unusable, then I will move to another brand. For the moment, because of the layout of one of my homes, the three Extremes do an awesome job, CAT6 wired all the way through.
Even if the Time Capsule's HDD goes, the first thing likely to happen, the router part should still be perfectly OK.
Bottom line: nothing is broken so far, just leave it alone to do its job.
Not necessarily true. As the article explained they’re going to stop support in five years. You’ll need the firmware/security updates to make them safe. Plus, at least another generation of new WiFi standards will surely be out by then.