Had a few opportunities recently. I will say that my approximation is still off.
Thought it would be coming out on the 60th card. "Ace of clubs" showed as dealer up card no less, around the 50th card.
One other obvious problem re: this relates to the multi-deck. I saw the "Ace of Clubs" and had to wonder if it was the one I saw. Seemed a little earlier, but that was the Ace, as it turned out.
I do think there is merit in this strategy. For sure, it's not full-proof. But I think it's worth the effort, if you worked out the conditional probabilities.
One other consideration from seeing loose cards. If you see 2 or 3 A/Ten, u should be prepared to depart that table very soon.