What a lovely hazy dreamworld you live in.
As a pp said, it's hilarious that you don't think the teen years will be difficult. You are in for a MASSIVE shock! And whilst you are a full-of-beans, mid 40s, energetic mum of toddlers now, you wait til the menopause hits you. It will hit for for six.
And when it DOES hit, you will have 2 primary school age children (close in age,) to deal with, at the age where most people have grandchildren! In addition, you will be dealing with teenager when you're almost 60. You sound very content and happy, but I wouldn't swap places with you for all the tea in China.
That's the thing... Some women of around 40 to 42, (who seem to think having a baby then is just wonderful,) forget that the youthful, energetic woman they are then is not the same person they will be when the child is school age/a teenager.
As I said, she will be a weary, frazzled, worn-down-by-menopause woman who feels every bit her age. And having to deal with school age children when you're a 50-something, frazzled, menopausal woman, and a teenager when you're knocking the door of 60, will be no picnic! Especially as you will very likely be dealing with ailing, elderly parents, and probably holding down a job too.
As I say, rather you than me.