The problem with long, continuous threads is it can become very hard to find a particular issue that was brought up on, say, page 52 of the thread when it's now on page 128. Shorter, more focused threads are arguably easier to search.
Though I've often found it frustratingly difficult to track down an individual post I saw somewhere on these forums months or a year ago, even using the search function. Especially if I don't remember exact wording or the title of the thread it was in.