Any saddle from a 15-20 year old bike is probably shot. Seats break down and wear out under me in a couple of seasons or about 10K miles. The foam gets soft, and the base tends to soften and sag in the middle, effectively taking pressure off the sitzbones, moving it forward, making the nose higher.
For me, numbness is the key indicator the saddle is wornout. When I started getting numb a couple of months ago, I checked the saddle by pressing down with my hand and found the foam and seat pan soft and flexy.
If a saddle flexes easily in the middle with hand pressure, it will become a hammock when you sit on it. Also, if the foam yields easily to thumb pressure, it's not going to support the weight of your sitzbones.
The identical replacement saddle felt much firmer, both the foam and the strength of the seat pan. For the first couple of rides, it felt like getting used to a new design saddle, but now all is well again.