Instead of using the Options API, you’d be better off using the Transients API, however in either case you’ll be polluting the *_options
table (even if you use transients with expiration times).
I’d possibly recommend using wp-session-manager plugin by EAMann’s which will allow you to use and store $_SESSION
data in a dedicated sessions database table that the plugin creates upon activation (or where it does not exist).
Reading: