That is unlikely to end well. Posts will need to be rebaked at some point in the future.
You can check one post with a link and see if a rebaked fixes it. You could then rebake just the ones with links.
Are you starting with one of the existing import scripts?
If you have a database dump, worst case you could extend your time line by putting up a placeholder page for a bit while you finish the import. It’ll be much worse to put up a botched import and allow people to add new posts, as it’s much, much easier to do an import on an empty site. Another solution would be to put up a new forum while you finish your script and then put the forum on hold for a bit while you run the final import to add the old data to the new forum.