In regards to membership, yes you can offer monthly packs to your client (for instance you wish to create for 3 months pack).
Firstly you will need to create a membership plan for 3 months. Kindly follow the steps below:
1. Go to Catalog >> Membership Tab
2. Click on "Create" button
3. It will ask to enter the Membership plan name, so you can for instance use the name as 3 months membership
4. After creating a membership plan, you can give your client more access by choosing options available
After following the above steps, you will need to follow the below steps to provide 3 months of membership to your client/customer
1. Go to Contacts and click on Members
2. Click on the "Create" button
3. Choose the client/member from the "Customer" search
4. Then click on Membership plan name that you created earlier
5. Now here you will have to choose the date under Subscription Schedule
6. Scroll down to the bottom of the page and click on Create Membership
Finally you will be able to add your client for 3 months membership.