How many spins do you give a machine to hit the bonus round?

I was playing the Dragon Link and it took around $100 plus the little win amount generated to initiate the bonus round via collecting 6 orbs in the generated reel. So close to 200 spins. 1 Cent Denomination , $0.50

I was playing the Dancing Drums and it took around $300 plus the win amount generated to initiate the bonus round. So close to 600 spins. 1 Cent Denomination , $0.88

I know slot machines are based on RNG but we never saw back to back Royal Flushes in Video
poker etc.