I think the subscriptions should all be options of a single product. The options will be the subscription length, you can adjust the price for these options for the longer subscription times.
So the product is the subscription, and the options the duration that control the price for the subscription.
As for the other problem you are having please describe exactly how you have created the item in your admin area and the options for it. What you are describing sounds like there may be some sort of server time out occurring when you are testing this.