Don't think of interrogatory answers as something to be forgotten after the initial stages of discovery are complete. Interrogatory answers often contain admissions that you can introduce into evidence at trial.
Part of every trial notebook is an "interrogatory" section (or more generally, a place for "admissions"). As you prepare for trial, go through your opponent's interrogatory answers and copy anything you might want to use later. These go into your trial notebook.
In most jurisdictions, interrogatory answers can be introduced by reading them to the jury. A party's interrogatory's answers can also be used to impeach the party's in-court testimony. As an admission, the answers will generally be an exception to the hearsay rule. But the answer will not be completely "binding" on the party; the jury will still be given a chance to weigh the in-court testimony against the interrogatory answer.
Partial source: Model Interrogatories §121 , by Kevin R. Culhane.