I don't think the number is zero, as seen in this thread. But overall I don't think humans are that altruistic. :) This is probably particularly true for user-oriented niche software (like the software in question, premium flight sim DLC). Some software in the past (eg Adobe Photoshop) that was marketed primarily for businesses possibly benefited a little from consumers pirating it, but again, that "benefit" is hard to quantify as well.
The reason I like the "time bomb" approach though is that I think it gives a bit of a "push" to anyone who is actually using your product extensively. If they aren't using your product enough to care to pay for it, it's probably not a big deal if they stop using your software. If the "time bomb" is at a reasonable period, I have serious doubts that they'd suddenly decide n months later (with no time bomb) that it's all of a sudden worth it to pay for software the have for "free".
I don't think niche products unfortunately can do what mass market products are doing these days... which is switching business models towards ones where piracy can be controlled a bit more or is less of a big deal. (Freemium / DLC, cloud-based, subscription-based, etc.) In fact the only alternative model I see for niche is the Kickstarter one where the consumers themselves front the initial business costs (which can work out for consumers sometimes, and not work out other times).
That still doesn't really tell you the answer though. The hypothesis is that pirates can be converted to users, but that doesn't necessarily happen immediately.
Suppose the product hits the piracy sites and 100,000 people download it. 5000 of them would have bought it, so you "lost" 5000 sales right away and you have your dip. But then over the course of the next year or two 7000 of those pirates realize they like the product and go on to buy it.
That's definitely a thing that happens, the question is what the real numbers are and whether they balance.
> I also know that there's one plugin developer (u-He) who has posted that the "time bomb" method he uses does drive sales the instant those "time bombs" go off.
Same problem here. Obviously you're going to get an uptick when the timer expires. But suppose you timebomb 100,000 people and as a result you immediately get 4000 sales, but then 96,000 people stop using your software. If 7000 of the 100,000 would eventually have paid you anyway, now you've just kicked 3000 of them out.