Was I being over cautious

I've been repairing a power amplifier. It has 24 large electrolytic capacitors, rated at 50 V and 15000 µF each, that run at about 48 V normally. It is 20 years old, and has been repaired in the past. I think that one short, that has been repaired, had caused one pair of capacitors to be damaged, as that pair was slightly bulged, but I have no idea how long they have been like that.

Anyhow, I bought a pair of new capacitors. I was slightly disappointed that I couldn't get a larger voltage in that size after another 20 years of development. The new capacitors are about 8 grams heavier (68 as opposed to 60) so I guessed that the old ones had gassed and dried out.

I measured the capacitance by charging them at 5 mA and timing how long it took to get to 40 V. I was surprised to find that the capacitance is still 15000 µF, same as the new ones.

Should I have saved my money and kept the old ones?

They might still have their rated capacity in microfarads, but their ESR value has probably gone trough the roof. You'd need a ESR meter to test that tough.