You can wait before suing on a patent

Latches is an equitable doctrine that says you can't know about a claim you could bring and then wait years before bringing a lawsuit.  The idea is that after a while, people should be able to rely on the fact that you haven't sued to indicate that you won't.  Last year SCOTUS found that latches doesn't apply to copyright cases.  Today they extended that holding to patent cases.  https://www.supremecourt.gov/opinions/16pdf/15-927_6j37.pdf

This is a rare pro-inventor win at the Supreme Court, and maybe (hopefully) an indication that the court is starting to feel it has dealt enough damage to the patent system.  Maybe.

But the bottom line is this:  If you invent a new device (say, a nanobot that monitors health) and you patent it, if another company copies your design and produces the device for 6 years, gaining dominant market position, you can sue them for the 6 years of back damages (the max the statute allows) and for an injunction and damages going forward.  They cannot say "he knew about it from day 1, allowed us to become big for 6 years, and then sued" as a defense.

This does not change the rule that if the infringer knows about the patent and still infringes, intentional infringement damages are available.

So the inventor's knowledge about infringement does not impair the ability to sue; the infringer's knowledge about infringement does harm the infringer's position in litigation.