I'd personally like to see a 'credit' system in place.
IE, once billed, 30 days of 'credit' are added to your account.
No matter how much or little you pay, after 24 hours, one
'credit' is deducted from your account.
This way, one can buy One month worth of credits (15$),
three months, six months, a years worth, etc.
Once the credits have been added to your account, you can
cancel your 'automatic renewal of subscription' and retain
membership until all credits on your account have expired.
This is the wishlist, after all...