The best dog in the world...... is it chancy for her age even tho she is fit n healthy?

WHAT ARE THE RISKS OF BREEDING MY 11 YEAR OLD JAK RUSSELL CROSS? SHE IS MY 2ND CHILD AND I WANT TO KEEP HER BLOODLINE GOING FOR OUR FAMILY WHO LOVE HER LOADS, I KNOW SHE IS AN OLD AGE BUT SHE IS UNBELIEVABLY FIT AND ACTIVE, AND ALSO THE MOST SPOILED DOG YOU WILL EVER MEEET. ANY ADVICE???