When you look at the current research on spaying and neutering, the AGE at which it's done turns out to be vitally important to your dog's future health. For example, your female dog should NOT be spayed at 6 months old.
Life Expectancy of Dogs and Cats. We hope our pets will be a part of our lives for many, many years but the fact is that the average life expectancy is 10-12 years for dogs and 10-14 years for cats. Older pets have very specific needs and are particularly susceptible in later years to cancer, arthritis, and dental disease.
Starting from about five months till ten months of age, female cats mature sexually and have their first estrous cycle. The average age for a cat going into heat is when they are around 6 months old. This is the time during the reproductive cycle when the female cat is most fertile and is most likely to conceive.