What's the reasoning behind replacing older capacitors?


Without getting too technical, What's the rationale of (I believe the term is re-capping)?Is it just a matter of newer is sonically "better" and if so in simple terms how?
The sound will become more detailed, less cloudy?I can understand why one would opt for an improved capacitor newer or different version after the values are matched.But if it's the same capacitor in sonic terms how does the usage and time effect the capacitor?Is it really a noticeable improvement or just trying to get that ole what I remember it used to sound like feeling back?
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