Nobody can give you an answer to this, except Google themself. Basicly, Google does not want you to ever "fix" links, they want people to link to you in a natural way. If it discovers a huge amounts of links in a short period of time, it will be suspicious of spam or link-buying, which could hurt your website. Whenever you trade or buy links, just be sure to not overdo it. There are no known limits. However, think for yourself what you would find "suspicious" if you were them. I generally try to not get more than 10 links a day and every 100 links i leave a couple of days between the links. This is working fine, and I never had any problems from Google's side for it.
But well, if you get 500 new links a day, you might might get hit by a bat in Google
Typically, the more your website is trusted, the easier Google will go over links. If you're sitting at PR 0, and you get 1000 instant links in a day, then expect the worst. However, if your website is at a high pagerank (for example youtube), then you can get thousands of links a day without any harm.