vinyl siding that was about 25 years old and yellowing and looked generally bad. He knew that I was a painter and asked if it could be painted? I said yes, then I contacted Sherwin for backup and they said yes.
What has to be done is: power wash the area thoroughly and get rid of grime, mold and other foreign things. Then prime it with a good exterior latex primer, then paint it with a good quality latex paint. I put on two coats of primer and two coats of finish coat and today, it still looks good, I repainted 10 years later as normal maintenance.
No problem. Latex paint is flexible and will give with the movement of the siding. This is important.
If the paint fails, its due to improper prep and poor quality paint.