Yes, CBSubs enables users to subscribe in order to be able to view a certain area of a site, and has even built-in access control (full ACL) with links and redirections for subscribing, without any core joomla or CB hacks.
Yes, CBSubs allows you to limit access by time period, maybe by individual "article" plans, or "user" subscription plans as well as automatic account enabling after payment has been accepted.
And Yes, CBSubs allows you much more than those two basic features.
Plus it's fully integrated and maintained with CB and Joomla (actually upcoming version CBSubs 1.1 (included in 1-year maintenance-included when buying) runs already on Joomla 1.6 beta !).
You can just buy its starter version (or any other CBSubs options) risk free with our 30-days money back warranty, you will be surprised by its possibilities, outlined in a detailed step-by-step manual which comes with it. You can extend number of users later if needed by paying just the difference in price on your profile here.