That would mean only your first IQ test ever can be meaningful. Every IQ test also teaches you a bit about the kind of thing IQ tests are looking for. I don't think any kind of a training is ever going to get you more than 10 points extra, but I'd be very surprised if at least a few points isn't doable.

There's also the fact that IQ tests need to be designed for a specific culture. Taking an IQ test for a very different culture is likely to cost you a couple of points. They're unavoidably subjective.

> I don't think any kind of a training is ever going to get you more than 10 points extra

I think it could easily be a lot more than 10 points. I once (ages ago) did an IQ test from a book and then 2 days later did another test from the same book and scored 27 points higher.

From this I concluded that either I had become vastly cleverer over those 2 days or that IQ tests weren't a good measure of intelligence.