You're absolutely right! There's something called the "Kolmogorov Zero-One Law" that says "the probability of something always happening again is either 100% or 0%". But usually, what people mean by this is that anything where the probability of it happening on any given day is some minimum nonzero amount (or a probability that goes to zero, but slowly enough that the probabilities add up over time), then it's going to happen eventually with probability 1.