I've had one for 3 years that has never flowered/gone red again - it's still healthy and I'm rubbish at throwing out healthy plants, though I may buy a new one this Christmas just to see if that provokes it
To encourage your poinsettia to flower for the Christmas holiday, you must carefully and precisely control the amount of light the plant receives each day.
To make a poinsettia flower for Christmas it must be kept in total darkness for fourteen hours each night during the months of October, November and early December. During that same time the plant should also receive six to eight hours of bright sunlight each day. This can be accomplished by moving the poinsettia to a dark closet each night between 5 PM and 8 AM, making sure that no light sneaks beneath the door. Or simply cover the plant with a large box overnight. No peeking! Even the smallest amount of stray light will upset the schedule and the poinsettia will not flower.
Strictly follow this schedule of six to eight hours of daylight and fourteen hours of total darkness for eight to ten weeks. Continue to fertilize the plant twice a month until mid December.
Oh my goodness, I'm slightly overwhelmed by that! <looks guiltily at poinsettia on the windowsill> Thank you for that, next year maybe for mine Actually would that work anytime of the year or do they have seasons? I could try and make it flower for my Feb birthday.