I think once rust begins setting in the hooks are on their way out and I wouldn't trust them implicitly. There have been times I've used hooks which had rusted a little, and I couldn't shake the feeling that if I hooked something good, they'd be weakened and break, so in a way it ruined my peace of mind
I always dry my lures off with a rag, and spray them with WD-40 to protect against rusting which seems to work quite well.