I would expect that if you buy feminized seeds from a good, reputable seed bank, you would not be at much of a risk for hermaphrodite plants. The only thing you know about these seeds is that it is POSSIBLE to make the plant go hermie. I would imagine that this is the case with most strains of cannabis already. Sometimes, to make feminized seeds, they use gibberelic acid on the plants. Sometimes, they wait until the plant is way past the normal flowering stage, and male flowers form. If either of these are the case, there's virtually no chance the progeny will have a greater risk of being hermaphrodites. Often, they sell feminized hybrids, in which case only one parent has to exhibit hermie traits. Sure, there'll sometimes be shady seed sellers who will have a female plant go hermie on them because of a hot grow room or something, then turn around and sell the seeds as "feminized" but among well-known seed banks, I think this is the exception, not the rule.

Still, from an economics standpoint, the feminized seeds are usually more than twice the cost of the regular ones. If you're growing indoors, you should have enough light to be able to plant twice as many seeds as you need, flower them, then ditch the males and grow the females. The only reason you might need feminized seeds is for a really small, occasional grow of one or two plants.