I work for a European multi-national. Some of my colleagues (sometimes the French ones too) are on all the time, and some colleagues are on-call during working hours only, and who take a month off every year (even some Americans!), during which time they are not available for anything. 1) I see no correlation between competence/getting things done and being on all the time. 2) Those who are on all the time tend to to be much more personally invested in work outcomes, so they are the ones who blow up every time some little thing doesn't go exactly their way. Overall, this makes these colleagues more difficult to accomplish things with, and I prefer the ones who have lives outside the company. This is basic time management. Of course, being asked (and paid) to be on call in case of an emergency is a different matter: I'm talking about normal work projects.