When's Prime Time on Twitter?

I had been thinking about when is prime time on Twitter and a post from Lisa Angelettie pushed me to think harder. We all want others to hear our questions or what we have to say. So we wonder when’s a good time to tweet for the best response.
My experience — and I am just one person who uses Twitter my way — shows that I receive great or many responses at all times of the day. But I do pay attention to time when it comes to weekends and weekday mornings.
Weekend Tweeting
On weekends, I post lightweight stuff because fewer people respond. So I used one weekend as an opportunity to ask people how to help a 10-year-old who dreads reading. Patty Bennett brilliantly suggested audio books. I asked son what he thought of that idea. His response? A hard head shaking. (Phooey.)
Joel Brodie told me about a kid, the same age as my son, who loves Bone. My guy does, too. But I still have to push him to read it and sometimes he needs to read specific books. I ordered the whole set (cheaper to do that than to buy the ones he doesn’t have yet). But what happens after he finishes that?
Weekday Morning Tweeting
Anyway, back on track. On weekday mornings, I also keep it light yet business-focused than personal. US time zones vary and people all begin work at different times.
Other Situations
In reviewing my @replies, I find I’ve gotten great responses throughout the day, but mainly 11:00am CST through 8:00pm CST.
The response rate also depends on who follows you. If you only have 100 followers, you might find a pattern. Someone with 2000+ followers has many high quality people who can catch a tweet any time of the day.
Do you participate in Twitter chats? The chats give you another great opportunity to join a conversation where your chances of getting noticed go up lots — unless you’re a lousy tweeter. If you need responses, tweet the request a couple of times throughout the day.
Also, remember to post the request on your blog and other networks like LinkedIn Answers. When you @reply someone, it won’t matter as much when you post those.
Most of us tend to check our @replies and time doesn’t matter unless it’s an urgent request. I went out of town last weekend and didn’t use Twitter at all. I read all of the @merylkevans tweets.
I try to check in Twitter a few times a day spending no more than a few minutes in each sitting (unless it’s a Twitter chat). I browse latest tweets, look at my following list and search for keywords. So not all of my Twitter action relies on the latest timeline.
Twitter knows no boundaries and time zones. Someone knowledgeable is always around at the time you send a tweet.
Is there such a thing as prime time on Twitter? Why or why not?