Hi - you know what your members want and need possibly more than anyone. But can I throw open the debate from a marketing point of view?
The WA payment levels are great, and I expect most people find they work well.
But with a subscription (or 'membership') there is no necessary link between the subscription fee and the payment schedule or the term (length) of the subscription.The concept of 'annual' is forgotten, just a convenient way of communicating the deal.
In other words, a new subscriber can subscribe for access to a website for any length of time. For instance, he may want to subscribe for the summer (boats and surfing). Or while taking exams (University crib sheets). Or when he is not traveling (off on holiday for a month). Or she will subscribe to the 'My Wedding' site for the six months leading up to the event. Or to the mother and baby site in the early part of pregnancy. Or to the 'What Car' site for two or three months while looking and choosing his next car.
So he will subscribe for three or six months, not twelve.If he or she is not offered alternative shorter terms subscriptions, he or she will not subscribe because half or more of the money will be wasted.
However, I understand this could be a minority view. There is no point offering a facility like various terms unless is increases the number of new memberships that come aboard. Perhaps there should be a 'Marketing' forum?! It's really about increasing revenue.
The choices would not overload the payment level page of a site because, for example, the owner would choose out of a maximum number of choices. The most successful marketers I work with choose either a free trial period or a low-cost introduction then six month terms. If the member cancells, his subscription simply stops when that six month period ends.Their payments page contains just that option because that works the best of all.