I was under the impression that resistors go long before most caps do, and leaking capacitors are a product of the old paper and oil ones that sound great but have limited life.
Most other caps don't leak as I understand it, they just stop working properly, with the so-called
noisy cap syndrome followed by complete failure.
That could be glue as dad911 questioned, I suggest getting the opinion from a wider audience at a forum I used to post at.
https://www.diyaudio.com/forums/index.php
That said I had new caps put in my old Dynaco solid state amp and it sounded better than before. My experience is bad caps degrade the quality (
slightly) then the music stops altogether.