Do you mean individual posts, or an entire thread of multiple posts:
If you mean individual post:
Its too long if your-
A) Ranting about something long after people already got the point. Once you get your point across its not necessary to keep hammering home the same point over and over.
B) Your covering TONS of different topics that need significant explanation within the same post. If a topic needs signficant detail then it deserves its own post.
C) Your failing to use proper paragraph break etiquette. A post that isn't really too long can feel too long to the reader if its displayed as one gigantic block of text.
If you mean thread:
Its too long if-
A) The same comments are being repeated more then twice. Anyone that cares about your opinion has already read it, anyone that doesn't obviously isn't going to read it, continuing to post your opinion with out new information to back it up is just a waste of space.
B) If its broken off into multiple topics. A good topic stays mostly on topic, if other ideas are brought up you can address them but if they require significant comments they probably deserve their own seperate thread. Too many good threads are derailed by tons of off-topic conversations.
c) The main topic is already answered but people continue to talk/argue. Once the main topic is sufficiently answered a thread can and usually should be ended. If you have something you'd like to argue about the response, make your own thread about it.
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