[dinkumthinkum]

I don’t know, it doesn’t seem like society is that fixed. It seems pretty malleable over the scale of decades.

[ElevenLathe]

On the scale of decades, your baby isn't a baby anymore and they can sleep however is convenient for them.

[TeMPOraL]

It changes, but it's not exactly easy for anyone to predict or control the direction of those changes. Also, this malleability is not what matters in this context - "over the scale of decades" isn't very helpful to the people alive today.