My previous Springer was out of as good of breeding as there was.. I didn't have her spayed as I thought I would some day have her bred. At 7 years old she came down with mammary cancer. I then had her spayed and cancer removed. At age nine cancer back and she had to be put down.
Vet said to reduce mammary cancer either spay before first heat or let have a liter of pups. I lost a really good dog, great behavior and super hunter.
The current Springer, we had spayed as per vets instructions. She gets a little heavy, and have had some periodic problems with urine. Personality never changed.