I rescued a yucca from a shop that I managed in the 70s. It is in a pot that has been changed for a larger pot as it grew older. It is now more than 45 years old and has never flowered; however, it resides in my conservatory in Dorset. It is now over 5 feet tall. Should I replant it in my garden (front north rear south)?
Lack of pollination is most likely the reason you have never seen the plant flower.
Without knowing the variety of your plant, I would hesitate to state weather you could plant outdoors. Perhaps you could move the plant outside for the warm summer days and then put back in the conservatory for winter.
Congratulations on growing this plant for this amount of time.