Don't forget, Gem, that some people actually like and only use the TdM (Tarot de Marseille). *shutters in horror at the thought*
Length of the reading: Depends on how many cards and how indepth you want the reading. Also if you're adding in the "extras" of
astrology, numology, etc, etc, etc...and NO you do NOT need to learn any of those to have a great indepth reading of tarot.
Some times it all depends on the question and/or the seeker...One person will be happy with one sentence tarot reading, another may want to know the ins and outs and whys and what fors and still not be happy.
Sleeping on the Question: Honestly I've never heard of and personally wouldn't do it because I'm likely to forget the question by that time. Sleeping on the reading I've heard of but again some reason as the question I won't do.
Now an interesting theory of questions though which I read somewhere is this:
Write down your question, then look over it and see what part you play in it. Are you (seeker in general) taking an active role in this question or are you excepting someone/thing else to be active? IE:
What will happen if I apply for this job? OR What can I do when I apply for this job?
The first while fine leaves a lot of wiggle room. The latter question make you responsible for applying for the job and if you want to add: to make me look like the best person? it gives you an even more defined and active role.