Every other company’s refer schemes let the link be used infinite times, ie you get paid for each new client referred. Affiliation is a business, if I write, say, an investing blog, I can hardly post a one-use-only referrer link. If it works well, then I will pay (FB, Google etc.) to promote the blog with the link on it.
Don’t mind the ‘free share’ concept (like RH) rather than a fixed amount, that’s like a little gamble, and adds to the interest (and tbh, speaking as a FT investor, probably works out cheaper).
Does the link initially take them to App Store to install the app?