I've also tried culantro, with little luck, though with that it just doesn't grow very fast at all. It is good in things that are cooked, as it seems that the flavor stays in the dish better than cilantro.
Funny thing about culantro - I actually rooted some one time! It never grew a crown, so it never could actually produce anything, but I did it when I was rooting just about every herb I could find in the Asian market.
I had sort of given up on cilantro, since it is available just about everywhere now, but the problem with that is storage. I'm sure just about everyone has pulled out a bag of cilantro that has turned to black slime in just a day or two, while another time it seems to store very well. As with all of the herbs, there is nothing better than snipping off what you need, right when you need it! I used to harvest all of my basil and Thai basil, and grind it up with just enough oil to make a paste, and froze this in popsicle forms, and pulled the little things out when I needed them in the winter. This was good, but not like fresh.
Speaking of climate control, my hydro systems are in my basement, at about 65Âº in the winter, and there is a very low wattage heater in each of them that keeps them at about 72-75Âº at all times. The plants seem to do well in this, and not as much water evaporates as in higher temps.