I once worked at a place that had 30 hour work weeks and 4 weeks vacation. That was great until we hired a guy who would take the CEO's slightest hint and run with it in his free time. After that, the execs would verbally "say" that sure, the expectation still was 30 hours/week, but the implicit expectation was use your free time to advance the company goals (expressed by praising all the goodies he and others who took the hint produced). And honestly it's hard to imagine a manager who isn't going to reward someone going over and above in their free time. And the result where suddenly no one has any free time is inevitable when that happens.