Brava, Deborah! You've packed a lot of value into a short post and 3 key points. 

I'd add one more point: What you tweet about is also a quick filter for others who may know nothing about you. If I'm checking new profiles on the weekend, I'll dig back to the work week. If your work week tweets aren't of value to me, then I'm gone.

PS: Of course, if I ever start tweeting in the middle of the night it'll be for the comaraderie of other insomniacs.