The setting is in the Scrape Tools tab. You will see it after checking the Scrape additional user details option:
what I recommend is what I also do, you should test, there are no fixed numbers, start with the default settings or lower, then start increasing day by day until you get a block then remember those settings and lower them by 20% then try again at one point you will start to get it and you will have some good intervales that work for you.