My 2cents, ditch the monthly plan, price it yearly instead. Monthly plans are for things you will actually use day to day like netflix, yearly are more like "insurance" products which is what this is, I think displaying the yearly option will be a better value proposition for people looking at it.
Second, I don't know what payment you're using, but seriously consider paypal if you're not already, because I'm pretty sure you can setup yearly recurring "subscriptions" on paypal and people are much more likely to keep their paypal funding sources up to date. So you're not going to have to nag them to update credit card info every couple years and they're less likely to have occasion to think "do I really want to pay for this", it'll just be pay automatically.