AFAIK, you could play on until winning in the winner's circle, and while the show was known as "$10,000 Pyramid" a WC win paid $10,000 added on to all money earned previously.
Contestants retired after winning in the WC, or losing to opponent in main game.
When it became "$20,000 Pyramid," your first trip to the winner's circle would earn $10,000 if successful, $15,000 on a second trip if successful, and on all future trips to the winner's circle, they'd be trying to win A TOTAL of $20,000! That was the most they'd take home!
Now, I'm not sure, for example, if a player won $500 with the "Big 7," in their first game, if they would win a total of $10,500 (or just $10k) if they won in the WC on their first attempt, but for sure, they retired immediately and WOULD NOT be able to try for $15k or $20K. (likewise, a $15k winner would retire!)
Maxene Fabe's book, published in 1979, mentioned that the record number of WC attempts, to that date, was seventeen!