Remove Terminated AD Accounts From SharePoint Groups

Hello SharePoint Fam,

I am wanting to create a pretty much 100% SharePoint Groups environment but one of my issues with groups is that a user name still seems to show months later in a group even though they are terminated and no longer with company.  This kind of drives managers crazy when they see old employee names so I was wondering is there anything that can be done to avoid this without needing to purchase a program like controlpoint that will help keep SharePoint groups clean/updated.  There will be hundreds of SharePoint groups created and i dont have the time to monitor groups all day long and I'm told this is bad when we are audited and terminated users still show up in groups.

Thanks for any help in advance