The oldest crappie i have ever aged is 9 years old in MO, out of a northern MO farm pond. you are probably very close with the 4 year old average, since harvest really targets 3 year old fish in most lakes, and fishing mortality is very high with crappie. Yes, it does change with regions. Way up north is way different, those fish tend to grow slower, but live longer. In the Southern reservoirs, crappie fish grow extremely fast, but live shorter lives.