LJ isn't searchable, but there is a partial solution to that, at least if you're using a Windoze machine. If you go to the ljArchive site, you'll find there what I think to be the best tool so far for archiving journals. The only irritation with it is that for it to run you'll need to install the .NET framework beforehand. There are links to the installer for that on the ljArchive page.
When you've archived your journal, it's very easy to search the archive. It'll find text in posts, comments, or in both.
Because it updates incrementally, the only time you'll sit around twiddling your thumbs is when it first downloads your journal; ever after, it just downloads any recent changes.