a-arm control arm shaft question

[68bowtie]

i'm wondering how one knows it's time to replace these. do they wear out or are they just replaced due to rust? or just the rubber seals failing? they seem to be just steel tubes. i'm planning my front suspension rebuild and i figure i'll replace them while i replace everything else "just because". UNLESS someone recommends inspecting, cleaning them up, and reinstalling them??

i want to fix everything that needs fixing, but it just seems like a simple part that wouldn't wear out. they are not too expensive, but they're not cheap either. any help is appreciated.