The process you describe is yet to happen e.g. the computers I have I don't want to replace unless they crash and burn. So in 5-ish years I believe vendors will slow down manufacturing indeed because many people do like I do: they get the newer more power-efficient stuff and then hold on to it for longer periods.
Again, I'm not saying what you're doing is bad, if everyone could fulfill their digital needs and wants out of second hand, that'd be awesome. I only wanted to point out that using less electricity isn't automatically better.
It's a balancing act between what we need to get our jobs done, what are our ergonomic preferences -- I have the so-called "lap desk" (basically two parallelepiped-shaped pillows and a well-designed plate with USB extensions to put on top of them) where I like to work on the couch or the bed -- and what is kinda sorta good for the planet.
I can't hyper-optimize only for the planet. I am doing my best but obviously everyone else has to help a little bit as well.
Thanks for entertaining this discussion, it was interesting.
To first order the upper bound for carbon cost of production/recycling is going to be a multiple of the energy required to melt the components. Call that multiple four: production of raw materials + reshaping in factory + recycling of materials at EOL + energy cost for assembly. So a rough upper limit of the energy to switch a computers would be four times the energy to heat the computer's mass in water (4 J/gC) up to the melting point of silica (1900 C), and a rough lower bound would be the same using the heat capcity and melting point of iron (10x lower heat capacity, 1500 C), and neglecting assembly. For 1 kg of material, that gives a range of 1.8 and 32 MJ. Now you can compare to the energy used. For myself, I'm on a 2 kg laptop that draws up to 250W, but conservatively 50W. That adds up to 32 MJ/kg in 400 h. If I can reduce the energy use by 5W with a new model, that will pay itself back in 2 years of workday computation. Crazy.
Caveat: there will be additional non-CO2 environmental costs. Most components are not recycled, and resource extraction is also environmentally damaging.
If it does then the people using them don't need to buy another one, new or refurbished. If they don't need to buy, other people can't sell as easily. If they can't sell as easily, they might use it longer, and not need/want to buy another one, old or refurbished, etc...
It's a whole market and if constructors see that the overall tendency is of using longer, they will get the signal that there can be less sales overall. And thus build less.
Everything we do is part of a larger system, and I believe we should understand what the system is like and how it works if we want to have a real impact.