If you were to make an assumption and say that mainline airliners will last 30 years and regionals 20 years, then here is where our fleet would retire by just adding 30 years and 20 years to their born on date.
As you see, the DC95 has outlasted this assumed retirement point, that's because, it's the DC9.
But you can see all the 752s and the domestic 763s that start to hit their retirement point. If A320s are in that mix then they will not be making the 30 year point, I assume.