... dunno how long it must, but I can say how long it does, which is basically forever these days. You put up a drunken selfie on a facebook equivalent when you're 18, it may lose you a job when you're 30, especially if you don't run damage control (which this guy apparently didn't, as others have noted). Six years is penny ante junk, and the proverbial shoe is on the metaphorical other foot -- it's a CEO getting shitlisted for previous life actions instead of a ground-level employee. Like it or not, this is basically the direction the US society is going.
I've been hearing a lot about "Total person" in the business classes I've been trudging through. Basically companies getting interested in what people do in their off time -- ostensibly so they can predict and work with outside-work disruptions in the workplace and make sure employees are managing a decent work/life balance (so they can work better, of course). But stuff like this is the other side of that. Companies in the states are increasingly saying, "Yes, if you want this job, I get to have input in your off hours." There's been folks fired because nicotine came up in a drug test -- not because they were smoking on the job, but because they were using nicotine products at all. Job applicants get regularly refused because something off-colored shows up in a facebook post or whathaveyou. This is basically the results of companies suddenly realizing what you do and what opinions you hold in your off time most definitely effects what you do (or, more accurately, what they can get from you) on the clock, and that if they want the best performance (from the company's perspective, anyway) they're going to have to meddle like goddamn, and they're going to judge like hell about what you did six, sixteen, sixty years ago. Regardless of whether it's good, bad, or ugly, it's how things are heading toward becoming in this place.