Hi @pascal_sapin! Maybe the Raspberry Pi isn’t the most suitable device for your use, it’s indeed a device « for tinkerers » that requires maintenance and a bit of follow-up, it’s not a consumer device at all…
In the community some people have switched to consumer machines to replace their Pi, mini-PCs at 100€ that you can find in stores, and there it’s « consumer-grade » hardware, under warranty, and it works without any particular issues… (and if it’s broken, return it to the manufacturer).
Maybe better suited to your need for long-term stability? 
@Tlse-vins made the switch recently.
We discuss it here :