I want to explain why I do not routinely have office hours within
30-minutes before a lecture.  When I lecture, I must go from my
office in Science and Technology #1 to Lecture Hall #1.  This is
a considerable walk, especially when you consider the fact that
I almost always have to carry (or schlepp) a load of material
that can include a telescope, slides, transparencies, globes, and
what some students have called "my balls."  The "balls" are many
different types and sizes of balls, from small soft rubber, to
tennis to basketballs, which I use for in-lecture demonstrations.
Obviously, it takes me time to go to the lecture hall with all
of my goodies in tow.  That is why I need about 30-minutes before
lectures to get everything together and get to the lecture hall,
not to mention logging-on to the electronic classroom equipment.