There are a number of ways to restrict how often your participants are allowed to be contacted across both scheduling and Pool emails. There are five types of Pool rules:
Each rule can be edited by the owner or admins, with variable conditions and actions. For example, let's say you wanted to make sure that no participants could be invited to be scheduled or receive a Pool email if they have reached $499 of incentives during this calendar year—you could set up a rule on Yearly Incentive Limits.
Or let's say you wanted to setup two cool down periods, so that anyone who has completed an interview can't be contacted for 2 weeks and anyone that's received a Pool email can't be contacted for 1 month—you can set rules on cool down periods: