Let's say each of those posts is 200 words, on average. You type 30 words a minute, which is probably generous. It takes you 6 minutes to type an article, let's add 4 for actually posting, editing, detecting music, setting pictures and icons, etc. I should probably throw in another minute or two for thinking about what it actually is you're going to say, but I've read some journals and I think we can safely leave that out for our purposes.
So, 10 minutes a post, times 50. 500 minutes a day just posting to LiveJournal. We haven't even started reading and replying to other people's journals. As windexcowboy stated, it could get to the point where all you have to talk about is posting to LiveJournal because that's all you do.
Go out. See a movie. Go driving. Hiking. Swimming. Read a freakin' book. 50 posts a day will be fine.