Five years. This guy sat through five years of WinZip nagging to get this screenshot. There's a reason companies don't really do shareware nowadays, and I think we've found it.
To be fair, old WinZip wasn't never really shareware. Given that it never stopped working, it was more akin to really naggy donationware, with a stern warning instead of the customary sad, human plea. The new version has a hard 45-day trial limit, which has rendered it more or less irrelevant in the face of better, free-er alternatives, including Windows' built-in archiving software. WinZip plumbed the depths of human stinginess and never found the bottom.
Anyway, five years is pretty impressive, but I'm willing to bet you guys can do better: Who among you, cheapskate Gizmodians, has hobo-hitched the WinZip train the furthest? [Reddit]
Update: Reader Ed G. wins by half a year. Keep sending! If there's a day one, Windows 98-having WinZip trial downloader out there, I want to find him.