The duration of an employer co-branding service can vary depending on various factors, including the scope and complexity of the collaboration, the specific goals and objectives, and the level of coordination required among the participating employers. Overall, the duration of an employer co-branding service can span several months, from the initial planning stages to the evaluation of its impact. It's important to note that the timeline can be influenced by external factors, such as the availability of resources, coordination among the participating employers, and any unforeseen challenges that may arise during the collaboration.