I've written several articles about 12-hour shift schedules. Here are links to the most popular ones:

1. https://www.shift-schedule-design.com/12-Hour_Shifts
    
2. https://www.shift-schedule-design.com/Blog?m8:post=12-hour-shifts-in-smaller-companies
    
3. https://www.shift-schedule-design.com/Blog?m8:post=matching-12-hour-shifts-to-your-workload-distribution
    
4. https://www.shift-schedule-design.com/Blog?m8:post=covering-absences-on-a-12-hour-shift-schedule
   
   
5. https://www.shift-schedule-design.com/Blog?m8:post=12-hour-shift-schedules-with-no-overtime

These 12-hr articles tend to focus on schedule effectiveness and efficiency, i.e. schedules that align the coverage with the workload and utilize the smallest number of employees. Other websites that offer free examples of different 12-hour patterns imply that these are good choices for anyone changing to longer shifts. Smaller groups with uneven workloads and staffing limitations should beware.

In this article, I'd like to address things that should be considered before making the change to 12-hour shifts.

1. Environment. Some jobs are simply too taxing to endure for more than 8 hours. Things like excessive heat, noise, toxins, or physical labor might preclude the use of longer shifts.
    
2. Productivity, quality and safety. Some tasks are too tedious or focused to continue for more than 8 hours. To accommodate 12-hr. shifts, these jobs would require extra breaks, job redesign, and/or periodic rotation to other positions to keep employees fresh.
    
3. Different patterns. With fixed 12-hr. shifts, there is no rule that says both shifts must work the same on-off pattern. In fact, some patterns that are great for the day shift (e.g., Pitman) are terrible for the night shift. We encourage clients to have each shift select its preferred shift independently.
    
4. Worker preferences. Although many employees are willing to work 12-hr. shifts in order to get more days off and more weekends off, not everyone is. Older workers, people with childcare or eldercare concerns, students, and those with 2^nd jobs often prefer 8-hour shifts.
    
5. Business issues. If the business runs 24/7 and has a steady workload at all times, 12-hour shifts can be a good choice. If the company uses fixed shifts, 12-hour fixed shifts are a little more efficient than 8-hour fixed shifts, which may mean a smaller headcount. If the workload is not steady, it may be necessary to use a combination of 8 and 12-hour shifts.
    
6. Absence coverage. If the organization has a high absence rate, 12-hour shifts might not be a good choice. That's because absences must be covered by someone who is scheduled to be off. This can defeat the extra days-off advantage of the longer shifts.
    
7. Pay policies. Most pay polices (e.g., holiday pay, vacations, sick leave, etc.) were written for 8-hour shifts. These polices need to be revised to reflect the 12-hr shifts. For example, with 8-hour shifts new employees get 10 days of vacation per calendar year (80 hours). If this policy was not modified before changing to 12-hour shifts, the new employees might get 120 hours of vacation per year.