Purchase-of-extension

Hi I have a question regarding the purchse of extension. I understand for monthly or yearly non premium plan, the extension is not provided and have to be purchased individually. Is the purchase of the extension one-off and it yours to keep indefinitely? Pls advise,

HI, I edited my query, actually what I want to clarify is this: if I purchase an extension, and I stopped my wealth-lab subscription for a period of time,, and when I re-subscribed to Wealth-lab again, is the extension still there or do I need to repurchase the extension again?