This is a great question, and we would need to do some additional benchmarking tests for character count within a single code block.
On average, it is about 40 lines per kB, so 1800 lines would equate to around 45kB.
We have performed benchmarking tests for how many total code blocks and how many pages/posts that the CJT plugin can handle. Once we investigate this further and learn its limitations, we will let you know.
Thinking further about this, maybe a benchmark page could be a good idea to have on the CJT website. 🙂