By default, in Salesforce, each object (or entity) is limited to 50 active workflow rules.
So, if you receive the error message displayed below when attempting to save a new rattle, fear not.
Just reference this Salesforce help article for guidance on how to increase the limit for your company's Salesforce instance.
If you open a support case, when giving the reason for the requested increase indicate that you are creating a workflow rule on a custom object for each customer and need the limit increased to 120 active workflow rules on each object.
Typically, the turnaround on these requests is less than 1 business day.