Would it be a good idea to sand and spray Rust prevention paint on an old drive shaft to keep it from rusting and causing U-Joints to fail?

Update: I remember a guy who was going to do some drive shaft repair telling me that on one of my trucks that he could see rust forming on the u-joints and that once you start seeing rust, that he recommends replacing them. So what if I sanded the rust off and sprayed some rust prevention primer and then paint on them?
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