https://assets.rte-france.com/prod/public/2020-07/Sch%C3%A9m...
"RTE France" is the entity in charge of those lines.
Plenty of lenghty docs for 10+ years plans:
https://www.rte-france.com/analyses-tendances-et-prospective...
Surprisingly, they also have lines that are 80-100 years old. I hadn't been following this story before, but upon first reading, I was shocked that infrastructure from 100 years ago was still in-place, original, and in operation. Now that seems normal.
My guess was that equipment would be replaced every 40-50 years, or at least renewed. The graph implies that the French policy is to replace after 45-70 years of service, but to allow older ones in limited cases. And they are saying the ones that are 70 years old need to be replaced in 5-10 years, so they allow up to 80 years.
I suppose that if the infrastructure is tested and maintained, and still cheap enough to maintain safely, there is no reason to replace it. As this story shows, you have to know your equipment and it's state of maintenance, and of course actively manage it safely and efficiently.