I've heard the opposite that they only get the full battery life prediction if you literally do nothing with them, i.e. just leave them idle (most companies do

I've heard the opposite that they only get the full battery life prediction if you literally do nothing with them, i.e. just leave them idle (most companies do this though - give the maximum battery life). The battery I have in my Lenovo was bought with the laptop, you could just upgrade it during the checkout process.