Little Frog is right, that most tolumnia bloom in the spring / early summer months. There's a lot of variability, though. I have a plant that bloomed back in December which surprised me this week by putting out a new spike! I've got another that started blooming at the same time in December and is still going strong! Still another plant bloomed last month or so, had flowers for about 2 weeks, and was done.
I'd say close to a month is average.
My experience has been that something like a cold snap can definitely shorten bloom longevity. Also, not enough humidity or too much heat. The flowers seem to last longest if they stay in an intermediate temperature at 50%- 70% humidity. Even moving them out of my growing case to enjoy on a countertop will often shorten the bloom life. I also seem to recall having read somewhere that fading blooms release chemical signals that can trigger other flowers nearby to also drop off. Because of that, I tend to remove fading / faded flowers right away, instead of letting them finish up on the plant. Maybe that helps, maybe not. But it helps the plants look nice!
Bear in mind, too, that plants which have been "forced" to spike / bloom in any way will often have a shorter bloom period.
Oh! And tolumnia seem to go through a mini-sulk when they change to new environments. So if your plant came from a greenhouse and is now living on a windowsill, it may take it a couple months to completely adjust to the new surroundings. You may find that next year's blooms are stupendous!