I don't know if any one ball joint is notably weaker than another. I've replaced crowd of them in every brand. Most recent completely separated lower ball joint I saw was a 2001 Mustang. The owner suggested that a speed bump in his apartment complex that he crossed while turning in and out of his parking space day after day might have been a contributing factor. Right there is where it broke apart so who knows?
I know he bought the car used about a year earlier. I found that it had been wrecked in that left front corner. I know we replaced the OEM ball joint. Was it damaged in the collision? Anyway...
Use, pot holes, egg shaped or out of balance tires, etc... are the wear factors for all suspension components.
As for grease... I wish I had a nickel for every blown out boot, huge gob of grease I've seen. Grease isn't a cure, too much does more harm than good.
