Thanks to everyone who responded. I had started to freak out a little yesterday when a Basenji site listed age span as 8 to 10 years. My B is 8 years old and has been with us for a little more than 4 years. I hardly remember what life was like before we got her! While she has calmed down some in the last year or so, she certainly doesn't act old.
I also want to give a broader thank you to everyone on this site. What a wonderful source of information and support!