After reading all of this I have been worried about speying Annabelle. So I chatted with our vet, he says he likes about 14-18 months. He said that Mammary Ca increases with every ovulation. But that she needs to be fully developed bone structure wise too. And the season has some importance. Dry weather is best for healing if you are able to choose surgery dates. I have had all my bitches previously speyed at 12 months, due to the fact I lost my darling Jessie to Ovarian Ca, paranoia on my behalf. But at the same token Abbey had a lot of bone issues, which the rest of her litter did not. She grew to be a very large bitch, about 140lbs. And she was quite osteoporotic. Which in humans happen when all the hormones reduce (menopause), so I still am at a loss as to what is PERFECT. I will just stick to doing it this coming Spring/Summer, when the weather is better.