It never makes sense, from a global warming point of view, to replace a notebook. This is because the market of notebooks is actually moving towards products with higher processing capacity, and therefore higher energy consumption. Existing ones should still be kept for 20 to 44 years for some sort of reasonable mitigation.
A 1-year lifetime extension of all notebooks in the EU would save 1.6 Mt CO2 per year by 2030, the equivalent of taking 870,000 cars off the roads.
https://eeb.org/wp-content/uploads/2019/09/Coolproducts-report.pdf