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Luckily those are easy to replace, they just bolt in. The upper ball joints require you to replace the whole upper control arm, but they are fairly easy to repalce too.
It's ok that you changed them 5 months apart. The ball joints really don't have a life span on them or anything, they go when they wanna go. The life of a ball joint mainly depends on how well it was greased when you got it(if no grease fitting), if it has a grease fitting to grease it, and how well/often you keep it greased if it does have a grease fitting.