Perhaps if you are diagnosing a specific problem.
If you can find one of the Zeo models that doesn't require access to the Zeo server, you'll get about 3 months out of the headband. Maybe a bit more. You can also carefully wash them with Woolite, but I haven't been able to get a signal off of mine.
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I just want to track accurately the quality of my sleep without much hassle. That's why I was considering zeo. If it doesn't last more than few months then it's not worth the investment on the second hand unit.