Q: Before I invest a week in a content idea, how do I know if it's evergreen or just a fad?

Q: Before I invest a week in a content idea, how do I know if it's evergreen or just a fad?

Short answer: ask if the same post would make sense in 12 months.

Longer answer:
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Strip out any reference to current audio, slang, or a named moment. Is there still a video? Then it's evergreen.
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Search the topic — if results span years, demand is durable.
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Fads answer 'what's happening now'; evergreen answers 'how do I' and 'why does.'
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Check if you could re-post it next quarter unchanged.

Verdict: invest a full week ONLY in evergreen — it pays rent for years. Fads deserve 30 minutes max. The 12-month test sorts them instantly: if it expires, it gets the cheap treatment.