Editor's hours are generally determined by the production schedule, and by the type of editorial position they have. Most salaried editors work in-house, dealing with production deadlines and the pressures of trying to produce accurate work. This is advantageous because they get to learn how the production works from the inside.
Advances in electronic communications have changed the work environment for writers and editors alike. Editors can do a lot of their editing from their homes or wherever they feel the most comfortable. This is both good and bad. Their schedules and hours are a lot more flexible and they have more independence.
Schedules and budgets are tight in a publishing house so a lot of employers don't want to risk new freelancing editors. They may be less likely to hire someone with no in-house experience. With experience, editors will know what they can handle and what projects might be too much. At some point they learn when to turn down a project. The most important thing is that editors use their time well and meet all deadlines. After all, they are working as part of a team and everyone must do their part.