Yes. You can run multiple anniversary eCard campaigns at the same time. For example, you can have a work anniversary eCard campaign for employees, another that celebrates a customer's first order with your company, and another for the first time a volunteer donated their time to your organization.
You might also need to subdivide those anniversary eCard campaigns into even smaller groups of contacts. For example, you might want a work anniversary eCard campaign for employees who have been with your organization for less than 5 years and another one for employees who have been with your organization for more than 5 years. The more you can segment your anniversary email lists, the more customized your anniversary eCard campaigns can be.
You can have an unlimited number of email lists and an unlimited number of automated email campaigns.