Unless you're writing with a kind of black spaghetti that can be sucked up again, a fluid graphite requires a solvent that must dry in air and dropping solvent on the dry writing would only make a gray smudge. The idea bears the tinge of a wish for magic with no mechanical physical capability worked out.

There's an entropy problem here--you can't return to the original state without an input of energy. This would definitely require an energy source (have to change batteries instead of loading lead).

First of all, your pencil will still run out unless you erase everything you write. I only erase a small percentage of what I write. Are you sure it's possible to make liquid lead? I'm a bit skeptical. How do you make an eraser that collects the lead? That's not the way erasers normally work.