In CX this is easily managed by the Qualtrics Directory options.  Looking at support pages I cannot see the equivalent for EX.  Contact Frequency Rules (qualtrics.com).  If no one else here can support, I’d speak to Support and see if this could be enabled, it may be limited by the licence you have.

For our quarterly pulse survey, we are creating a stratified sample of our employees outside of Qualtrics each month (using the Knime tool).  We have over 85K employees globally so we use Region and Business Group as the strata to ensure that the sampling is consistent (as much as possible anyway);  i.e.: regions and BGs with more employees don’t end up dominating the sample.

We then upload the sample into our pulse survey project and distribute it monthly. Using this method we reach each employee on average about 2 times a year.  Although we distribute the survey monthly we report the results quarterly (inline with other employee metrics).

We really couldn’t find a better way to perform sampling in EX but I know sometimes CX has features that EX doesn’t.  You may want to look into using Knime or a similiar external tool to create  your sample.