And yet my 2.9 kg Dell Precision 7540 lasts 2 - 3 hours of office work. Didn't 3 kg laptops from 20 years back last about the same time? I don't think they last

And yet my 2.9 kg Dell Precision 7540 lasts 2 - 3 hours of office work. Didn't 3 kg laptops from 20 years back last about the same time? I don't think they lasted less than a hour. Or were they much heavier?