Never. I have a Macbook air and I only close it without powering it off.
I reboot from windows to linux, but essentially never turn it off unless I have very good reason--traveling, for instance.
I just turn my notebook into sleep.
Every night or while traveling
Maybe around once a month, on a MacBook Air.
Nope
Yes. I only use a laptop when work requires me to travel. The vast majority of its life it spends turned off and locked up in my desk.
Never
Yes, whenever I'm not using it.
From boot menu to booted is only about 6 seconds (gradually tweaking that to be faster).