Hi Maryke,
With s2Member Pro, the Pro-Forms feature allows you to configure the
rrt= shortcode attribute:
rrt="" Recurring Times ( i.e. a fixed number of installments ). Only valid w/ Membership Level Access. When unspecified, any recurring charges will remain ongoing until cancelled, or until payments start failing. If this is set to 1 or higher the regular recurring charges will only continue for X billing cycles, depending on what you specify. This is only valid when rr="1" for recurring "Subscriptions". Please note that a fixed number of installments, also means a fixed period of access. If a Customer's billing is monthly, and you set rrt="3", billing will continue for only 3 monthly installments. After that, billing would stop, and their access to the site would be revoked as well ( based on your EOT Behavior setting under: s2Member -> PayPal® Options ).
However, as that explains, a fixed number of installments also means a fixed period of access.
If you created a weekly subscription button and set
rrt="4", your members would be charged 4 times and then their access would be revoked (which, in this case means after 1 month -- not what you want).
The only other solution I can think of is to use a Buy Now button to offer 6 months of access.
The Buy Now button wouldn't give you the 4 installment payments you're looking to offer, but it would mean that you could sell 6 months of access with one payment and the users account would automatically expire after six months.