I hope this physicist would not surprise you too much. I do not know what kind of long division problems invovled, but there are actually many different concepts and levels of understanding for kids (for us, we have forgotten because we have generalized them into just a few!) in long division. However, I am a little bothered by 4-digit. I hope it does not involve a 4-digit divisor, that I will call "child abuse"!
You wrote: often is) taken to an extreme by teachers who don't have any better ideas on how to teach (*my* son was just assigned 32 problems on long division of 4 digit numbers, due tomorrow, and sans calculator. I'm doing my best to convince him that math is in fact interesting, but sometimes it's a real battle.). My feeling is that once a student has been able to do five (or ten; the number (and it's not exact) depends on the kind of problem, and on the student) problems of a certain type correctly and *without getting confused* at any point, then they are about 99% as good as they will ever be at this type of problem, and assigning an additional 3000 so that they can get to the 99.5% level borders on child abuse.