However, despite the risk of still appearing to be continuing the 'attack', it's really not about how "long" one speaks. It's mostly about speaking in a way that enables exchange in conversation, by allowing counterpoints to enter, vs not doing so, and making multiple unrebuttable statements in a row, completely monopolizing and derailing the conversation.
E.g. (Good:) "I think the government should stay off the gold standard, so that the pound can reach a level that can keep our exports competitive. [Pause]"
vs
(Bad:) "I think the government should stay off the gold standard, partly because our exports, well, you know how women are always underpaid compared to men, 70c on the dollar, which by the way would have been stronger than the pound, had only the government not treated the whole case with the federal reserve so shabilly, almost as shabbily as cryptocurrencies, which by the way are the future, only a fool would not invest, filecoin in particular; have you shared drive space to the IPFS yet?"
There. 10 seconds max. But good luck discussing the gold standard after this. Or the pay gap. Or the Federal reserve. I wanted to interrupt myself like 5 times during that sentence.
Obviously the commonest example is people speaking in run-on sentences like in the example above, but this is not the only way to make yourself uninterruptible. An equally annoying variant of this is where sometimes people actually pause at a natural point for counterpoint, but when you attempt to 'reply' or offer your counterpoint, they continue as if to say "the pause was not an invitation", effectively transforming the counterpoint into an interruption. This is one of those cases where person A then claims they were interrupted, but in fact person B could validly claim the same. This is often a display of power, as it has the effect that A 'paces' the conversation, painting a bad picture about B 'the interruptor' in the room, and causes B (and all others) to vastly delay or completely bury any further attempts at counterpoint when the opportunity naturally arises.
E.g.
A: The report needs to be ready by Monday [Pause].
B: Of course, but we still need to consider--
A: ... since any later than Monday -- excuse me, B -- will delay the whole project by a Month. [Pause].
B: Yes. Of course. But before we submit we really should--
A: ... and if the project is delayed -- excuse me again, B-- by a month, we'll be REALLY late then [long thoughtful pause].
B: ... y ... yes. I do think however that it we really ought--
A: ... and good heavens -- B, please let me finish-- if we delay, what will I tell Bob? So, we're all agreed? Good. We'd better press on too, we're running out of time. B, you wanted to say something?
B: ... no, no. All good. Let's move on.Also, not that it's very important, but if you can read out that passage of yours in under 10 seconds I'll give you a prize!
But on a more serious note: I tried that too. Doesn't work with certain people. Some get even angry, give you a "Let me finish talking!" lecture and continue talking for literal hours. What i started doing, was to just leave. Like, physically leave. Now that probably won't work if you're in a meeting or talking to the boss, so use with care.
Most of the time, people aren't aware they're being rude, but will be offended if you try a passive-aggressive way of implying this is the case.
edit: unless they're a "serial interrupter" as in sibling comment, we have one of those