@SW-User There’s no set time....you just can’t know (her husband was 66 when he married her). Don’t think it’s too late....especially at your age (even I was older than you are when I got married).
It would depend on the relationship....I knew my wife about 3 years when we married, but I don’t know that there’s a cutoff time (it just has to feel right). We waited until I graduated from Law School.