Whenever someone uses your link to make an eligible purchase, you get paid!
When someone clicks your link to a store and then buys a different product, you can still get credit! In fact, in many cases, if the user doesn't buy anything today, but they decide to buy something tomorrow (or even next week), you will still get credit! Every store sets their policies, so it's hard for us to give guidance on what to expect. But you can rest assured that as long as the person who clicked your link is on the same device and buying from the same store, you're very likely to get credit for their purchase.