I've realised I have a vague/subconscious limit of approx 4/5 pages of responses following an initial OP ...if an OP hasn't come back to respond by then, I guess I start to wonder whether I really want to get involved commenting. But I've seen so many threads recently with a single post from the OP and 15+ pages of responses (often on quite...contentious stuff), so maybe my approach isn't the norm? I guess it comes down to whether you're responding to connect with/advise the OP, or whether you look at it more as a precursor to a general discussion (and of course on how much you value OP updates, but for me that sort of depends on the topic).