40 months after submitting the I-751 (we had been waiting for an interview since early 2019), my wife applied for citizenship. 4 months later both I-751 and N-400 were approved during a combo interview. six weeks after the interview, she took the citizenship oath and became a citizen.
In summary, it took 13 months for approval of the CR-1. It took 44 months for approval of the I-751. It took 4 months for approval of the N-400