Retiring a doe from breeding

I was just wondering, what you guys think is the best age to "retire" a doe (female goat) from breeding? Some say 11-12 years. What's your experience? My eldest doe is 11 now and I don't think we will breed her again. She is a virgin milker so there's really no need to now that she has given birth to two girls so the her virgin milker genes will hopefully live on.
Here's a picture of our doe on her last "date".

Beautiful goats!

I think it gets a bit risky after that age. She looks healthy, and hasn't had many kids, so she would probably be right to have another date, but there are more chances of something going wrong as she gets older, so it's so good that you've passed her virgin milker genes on to her daughters, as you can just breed more from them.