I'll happily mentor anyone who wants mentoring, and most of that goes on by internet rather than face to face.
Then you start another book and suddenly the galley proofs of the last one come in and you have to wrench your attention away from what you're writing and try to remember what you were thinking when you wrote the previous one.
Agents will read unpublished work because they might make money, and that's their job. It isn't mine.
One book at a time... though I'm usually doing the research for others while I'm writing, but that sort of research is fairly desultory and I like to stick to the book being written - and writing a book concentrates the mind so the research is more productive.
What I mean by that is that the point of life, as I see it, is not to write books or scale mountains or sail oceans, but to achieve happiness, and preferably an unselfish happiness.
Of course some days are easier than others, but my worst day is better than being in most humdrum occupations.