Tango was spayed at 7 months, much sooner than I'd have liked. Tia was spayed at 6 months, Morgan at 10 weeks (which IMO is waaay too young), and Winston was neutered at 6 1/2 years (before we adopted him).

I prefer to spay dogs after their first heat and my age preference is around 18 months or so to allow for proper growth and development. All of my future dogs will be spayed after their first heats, and somewhere between this age if I'm not showing them. If I ever have another male, the same age will apply.