auth->check_feature and different expires

I was now trying the snapshot with the aim of providing a different expire for eg user kris (admin), than anoter user (not admin). So I defined the Example_Auth (eg the admin only showoff) with a lifetime=1, and a example_default_auth with a lifetime of 3 minutes. But when I am visiting, as admin, a page that is for default_auth, my lifetime gets extended to that of the defauth class, because it's in the persistent $auth->auth array. While I would be able to keep my 'admin' one. So maybe the check feature should also check, if different auth feature, also recalclate the $auth->auth[exp] inherited. Gian