Why electrons in a wire do not run out and the wires do not deteriorate

Where do electrons come from in a conductor and why do they not run out? Based on common sense and knowledge of the planetary model of the atom, the number of electrons in an atom is limited. Then, when the ordered movement of particles, that is, electrons, is formed, they should simply be washed away like sand is washed out of a pipe. And why then do the properties of the conductor not degrade if all the electrons leave?
1:04 - Once again we recall the definition of electric current
1:35 - What is electron gas or free electrons in metals
2:38 - The structure of the atom and the reason for the appearance of free electrons
4:27 - Why don’t these electrons run out and what is the model here?
5:55 - Can electrons move from conductor to conductor at the point of contact?
6:05 - What does a generator do?
6:33 - Does a conductor suffer from constant current flow?
These are questions that, unfortunately, the school curriculum never answers. Meanwhile, the questions are very important and interesting! Let's try to understand these points together and define in a simple form what an electron gas is and how it turns out that it is always present in a conductor. What exactly happens when current is transferred from one point to another and whether an electrical wire can wear out due to the passage of current.