Adding some more details:
Basically the Wanikani team run a discount every Christmas for the lifetime subscription (it goes from $300 to $200). Also, in case you decide to upgrade while you’re still subscribed, they discount what you have yet to use from your subscription into your total to pay for the subscription upgrade. If you subscribe right now for a year, you might get around an extra $40 discount in December for the lifetime.
This promotion is not a guarantee, but they seem to do it every year. They don’t confirm it for the drama
I do think this is the best option, no matter how much time you’ll use Wanikani for. Some people reach level 60 in 1 year, for most it takes around 2 years. However, most people never even get to level 60. Wanikani requires discipline