Kupocake
What people want is a constant stream of new information/images/memes, and they get upset when they've refreshed their Dashboard and nothing new shows up within the last 15 minutes. That's the reality of the average Tumblr-user, and I try to accommodate that without destroying my sanity. So, 2-3 times in a single day has been good for me so far.
And I do try to make my updates meaningful or interesting.
I haven't ventured into Twitter territory, I feel it's a bit premature for my comic so far, but Tumblr's been fantastic for pageviews, at least in my case.
I guess I should face the reality that Tumblr users really do spend their day checking Tumblr every 10-30 minutes ._. I'm the opposite, I try to keep my dash clean enough that I only need to check it two-three times a day and not have to go to page 2.
I'll aim for daily updates, but if I happen to have extra stuff to post, I guess there's no reason to hesitate? I think that's a more productive way for me to look at it than "oh crap I'm spamming" :
D
Twitter's been great for me! I haven't kept detailed stats, but at least for Livestream, it seems like Twitter is the next best thing to an LS announcement along with a page update.
People's twitter feeds automatically filter out conversations with other people, so it's easy to use Twitter for both chatting (though I do try to keep it minimal) and updates/announcements.