If Vod is correct about the number of posts, that would mean taking over 5,000 days assuming one post was checked per second.
You can download one page (up to 20 posts) per second. In ideal circumstances this would take just a month, in reality probably 2 months.
Ahh yes, that is my mistake. I am not sure what the distribution of page lengths look like, but some pages are shorter than 20 posts, for example for threads with 21 posts, the second page will have one post, and a thread with 3 posts will have one page with 3 posts. So long as the average thread length is above 30 posts, it would take an upper bound of 2 months to scrap all the posts.
he problem was the very large number of BS-posts like "good project".
You should be able to filter these types of posts out. Ditto with posts under a certain length that would not be reasonably plagiarism.