Edit: The legal term appears to be "the doctrine of latches"
However, the Supreme Court has recently (March) said that laches is no defense to patent infringement. [2]
[1] https://en.wikipedia.org/wiki/Laches_(equity)
[2] http://www.ipwatchdog.com/2017/03/22/supreme-court-says-lach...
Edit: The legal term appears to be "the doctrine of latches"