I have 2 which have started to flower but are quite old and straggly again. I have previously pulled off growth after flowering, at leaf joints leaving only a 6" framework. Then used some of the leaves to propogate. Also repot original into fresh compost , rootball can also be trimmed without Ill effects.

I have one that's over 10 years old and it only gets more and more glorious with each passing year growing into a huge umbrella shape and blooms around the holidays. Ok, my cat knocked if over a couple times and broke off a huge piece, but it's very forgiving and all grew back. It basically just sits there in the corner and I barely do anything to it except a little water every couple weeks, but it's a succulent and doesn't need much water, esp during the colder months. Bright indirect light & good air movement around it. Keep it on the dry side and not much fertilizer.

Thank you Barbarak and Bathgate for your reply

I have a couple of descendants from one I had in the 1950s which I keep for sentimental reasons. Repot occasionally in a peaty type compost - remember they are epiphytes so grow in the leaf litter left in crannies in trees. Take Barbara'a advice and take a few cuttings to rejuvenate it, though best to wait until the Spring if you can. In the meantime try just giving it a feed.
It has be said that varieties have greatly improved since those days though, and you might like to try one or two of those too. Let me know if you want any cuttings.

These plants are very sensitive to temperature and it's the shortening of days & cooler night temperatures which signal it's time to flower. If the plant is kept in a heated room with barely a difference between day & night temperatures, the plant may abort the bloom cycle altogether and the buds will drop off.

Thank you Steragram and Bathgate for your valuable advice.