Six feet was the longest corn snake on record (to my understanding), but most will grow between 3-5 feet, and will take 4-7 years for them to reach this length. It makes sense that they continue to grow, but from what I've read, they can live 15-20 years, so if in 5 years they're 5 feet long, they can't possibly grow much longer in the next 10 (if that makes sense).
Mine is 3-4 months old and is just over 20 inches. Maybe 21" (was hatched at around 15"). You sure about that size/age there, seawin? lol