Emphasizing that even though discovery had not closed, the court unanimously affirmed a district court's decision not to permit amendment of contentions relating to infringement and claim construction. The cae is Kruse Techn. Partnerships v. VW, opinion by Judge Linn (joined by Judge Newmann). Judge Wallach dissented on claim construction grounds.
This is one of those tough issues: you have to get your claim construction contention correct, early, but… even what the district court holds has a large chance of being wrong. Bottom line is amend early, though not often.