Three things may help…
1) You can cretae different member levels – like Visitor, Irregular, Regular, Member – and then the people edit page allow you to put in dates.
2) Follow Up Funnels on the people page allow you to create steps in membership process that can be setup.
3) There is a notes field for people too.
You can also deactivate people, so they stay in the directory but are not available for email, sms or in the phone directory shortcodes.