You did even not tell us WHY you consider to purchase a new notebook.Are you just searching a "reason" to buy a new one?
as for the lifespan of the MP 12" : Nobody is a prophet. It does not at all seem that apple wants to sell reliable and sturdy computers any more. You are talking about the weather in 2020-12-15 ? We really don´t know..
So - your decision is made.

She is intelligent...
Why purchasing a new one?? Don´t see the rationale…
If you are working all day with your computer as a NON-power-user (concerning performance) - it is all about personal ERGONOMICS … nothing else.
Take apple Care - so, you are comfortable for at least 3 Years.
I played a little bit with the MP 12" in the store… and for me it is just a shiny glittering "have to show my friends" - and shurely not a working-horse at all.