Mystica,
Unfortunately, EOT time only works in two ways.
NOTE: THIS ONLY APPLIES IF YOU ARE USING BUY NOW TRANSACTIONS(FIXED TERM). IF USING RECURRING OPTIONS THE SECOND(two) ONE IS THE ONE THE SYSTEM USES BY DEFAULT AND CANT BE CHANGED IN ANY SETTINGS.
ONE: everytime a user purchases something, the eot time gets reset to the new eot of whatever they just purchased.
TWO: everytime a user purchases something, the eot gets extended the old eot plus the new eot. ex. he had 3 months left then he bought something that has 4 months access. he now has 7 months remaining.
These options can be selected by going to s2member -> PayPal Options -> Automatic EOT Behavior
So in short, what you need is not something that can be accomplished with the plugin system by default.
It can be accomplished through some custom coding and database work by any freelancer like me or others.
Feel free to contact me for hire.
Thanks.
Jason K.