What is the longest you know someone had survived with congestive heart failure?

A few Decades. Due to varying degrees of CHF & of adherence to treatment, there are varying degrees of survival. A mild CHF and excellent adherence to therapy in younger patients carries a relatively good prognosis. The opposite is certainly true too!
28 years. That is how long I have been a physician. I am certain there are a few people who have survived longer. Depends on the cause of congestive heart failure.