Babs, you'll be keeping milking records I presume... When the girls get to the point that their production starts dropping off, that's the time to re-home them. The new owner can still get several good years out of them yet. So 1 doe might need to go at 6 years while another might be 7 or even 8. You'll be able to show the new owner the documented production so they'll know that the age number is just that... a number, and the goat is still very healthy and still able to produce.