That sounds like a pretty typical age recommendation for spaying.
I have a blue heeler mix (we *think* mixed with border collie) I got from a rescue organization last summer. She is, hands down, the sweetest, gentlest, most patient dog I have ever met in my entire life. SO good with the kids, I can't even believe it.
Mine thinks she's a cat.
She can't handle it if she's not sitting on somebody, typically when it's the most irritating time possible.