This post isn't about dielectric absorption either but it does talk about dissipation factor of bad caps.
I have a vintage Pioneer TX-500 tuner that I picked up off the curb more than 10 years ago.
I've used it for years as a shop tuner.
The AM section had high second-order distortion and it had begun to sound really funky on FM.
I felt like soldering today and it needed a re-cap.
The date codes of most of the caps were July 1969: 49 years ago this month.
Six were United Chemcon, nine were Nichicons.
Measurement of the 49-year-old capacitors:
Of the 15 caps I replaced, 12 still measured within tolerance at 100 Hz.
A value reading, based on low frequencies, would have shown most caps to be "good."
Their 100 Hz Dissipation Factor typically ranged from 0.200 to 1 vs. a modern electrolytic of similar size measuring <<0.04.
Based on DF, but not value, all were bad.
Using a 1 kHz measurement frequency and declaring caps measuring 1/2 their printed value "bad" the numbers change significantly.
11 of 15 caps were 1/2 their value at 1 kHz.
Measurement frequency or LF DF tell a much different story than a simple low frequency value measurement.
This may explain years ago after re-capping an MCI JH-500 why we all were stunned at the mid-range improvement after finishing the job.
We were expecting a tighter low end, which we got, but the entire console "opened up" post-recap.
I didn't have the LCR meter then...
I think I'm going to throw these caps in a poly bag and FFT them some day.
BTW KMN we used inductors (2 for balance) in the Rg leads of Joe Neil's "Wayne Mic Preamp." viewtopic.php?f=7&t=339
The object was to limit HF gain - I think the -3dB point at max gain was about 80 kHz.
We did that to control differential gain since it was going to be used with long (>500 feet) lines.