Darci Kistler will retire next year: http://www.nytimes.com/2009/02/05/arts/ ... 5ball.html
Sad to say, I think she's long past retiring gracefully - I haven't seen the company recently, but even a few years ago, I found her dancing limited and though that she was most frequently cast in roles that were no longer appropriate.
It's too bad because she is such a talented and elegant dancer. However, judging by comments here and elsewhere, too many people are going to remember her by the fading performances of the last five years rather than the glorious ones of her earlier days.
I do think it must be hard, especially for the women, at NYCB, because perhaps the most of any company, the repertory offers little in the way of character roles for a mature dancer. Thus a ballerina who has much left to offer artistically, but because of injuries/age is fading technically, doesn't have an easy way to transition out.
And I think the artistic staff hasn't always been honest and/or helpful in making casting decisions. I saw Kistler in a number of roles that she simply wasn't capable of doing technically, and once in the last few years of her career when she'd returned from maternity leave (I think), I saw Kyra Nichols as Titania in Midsummer Night's Dream when it was painfully clear there was no way she could do all the choreography. From the beginning of the pas de deux, you could tell the jumps to shoulder sits were not going to happen.
I think the best examples of well timed retirements were Margaret Tracey, Peter Boal and especially Damian Woetzel. They all were still well capable when they retired, so my memories are of strong, capable dancers.