I am deep into custom keyboards but I only buy ones with hot swappable switches. Some keys like AWSDEHJKL etc are bound to fail sooner than others.
And all of us have owned multiple keyboards that have lasted for years of daily heavy use without a single key failing. Even the $30 membranes you could buy at $local_retailer didn't fail in a month.
The mechanical keyboard hobby takes patience; just look at firmware customization: testing litterally requires keystrokes.
I'm on a Mac keyboard bent for the very reason, actually,
Mouse firmware sounds very cool, though. If you could access a layer by holding down a central button, that could open up neat possibilities.