If plants do not want to go dormant, there is no need to force it to do it. I believe that it is depending were original mother bulb is coming from (if it come from a cold country, it will be dormant in winter, if it come from a tropic country/state, it will stay green all winter, as long as you bring it indoors, kep temperature above 50 F and water it as needed.
I also found that repotting into a new soil every 3-4 years keep bulbs healthy, with good growth and no rotting. It is also not a good idea to grow bulb in overcrowded pot. If you grow them in a plastic pot, and see that pot start to deform, it is a good time for repot.
