I personally believe that, in some cases and depending on the product, placing urgency on the user can yield positive outcomes. This also grants you additional freedoms to "nudge" the user, simple example, "setup an account and earn an extra week of trial".
Good work and good luck, keep experimenting and measuring.
Definitely going annual as well - tempted to go only annual, but we'll see.
Annual plan only available after 6 months of membership?
While I understand that sounds counterintuitive, if not odd, it:
a) offers an incentive to stay.
b) with that goal line in mind, the offer of annual when getting there has special meaning. As opposed to a random "you've stayed. You must be happy. Wanna go annual?"
Again. I hear what you're saying, but in a nudge-y / Hooked sorta way it might work.
I took it.