Also, assuming the guy has been in the league 2+ years, you are going to notice how he has improved from season to season. Knowing that the greatest improvement occurs in the first 2 seasons, you should have a pretty good idea of where he is going. After 4 full seasons, you're not going to see much improvement regardless of age. Like Mike said, even if you are a tiny bit off, it shouldn't hurt anything. Keep in mind, even 20 advanced scouting is not exact, its still just an estimate