If you use the access restrictions based on levels, then access will be incremental and a level 2 user will have access to a level 1 content.
WP Admin -> s2Member -> Restriction OptionsNow, you can use levels and instead of the access restrictions, use conditionals to decide what content to show.
WP Admin -> s2Member -> API / Scripting -> Simple/Shortcode Conditionals or Advanced/PHP ConditionalsNow, an automatic EOT behavior, as it's implemented in the current release, will affect all access you sold the person.
WP Admin -> s2Member -> PayPal Options -> Auto EOT BehaviorIf you want to do something more custom, I'd say you disable the auto behavior and instead work with conditionals only.
You may want to look at using custom capabilities too, instead of just levels.
http://www.s2member.com/custom-capabilities-video/I hope this helps!