According to the House Rabbit Society...
Rabbits often live into their second decade. Early House Rabbit Society literature reported rabbis living only 4 to 5 years. This misconception was likely because of rabbis dying at an early age due to poor management, rich diets and lack of ovariohysterectomy (spaying). In our experience, 10- to 12-year-old rabbits are not uncommon, and rabbits as old as 14 years have been presented to our practice. We have not as yet determined the record-breaking age for a rabbit, but there are anecdotal reports of rabbits living 16 to 18 years.
http://www.rabbit.org/chapters/san-d...k/elderly.html
I hope Billie is with your family for many more years!