It would be really helpful to know what seats from what car you are referring to. Naturally, the older the seats the poorer condition the seat foam will be in. More likely the culprit is poor workmanship and/or poor seat foam rather than poor quality leather. The leather should have been glued to the sew foam and sewed around the edges to the sew foam. When you have leather seats done, you should ask for either full grain or top grain leather, and have that documented. It's a lot easier to have leather turn out well over fiberglass than over foam, but whoever did your seats should have explained to you that working over 30 year old seat foam is not conducive to good quality seats. I won't do leather seats (or any seats for that matter) unless my customer is aware of these things before I start.
No one lives forever, the trick is creating something that will.