That's an apples and oranges comparison.

While the timeline isn't explicitly stated, free refills are implied that it's for the duration of your visit. In fact you can see the implication given that's how it's used most of the time.

Telling someone they'll get "lifetime" access for a one-time payment is not the same.

In fact, if I was told I had purchased lifetime free refills, I would expect I could obtain a refill during any visit without purchase.