Depending on what publication you read and what person you talk to, you'll find that most say the tempurature should be between 74-76 degrees, ideally.
Of course, plants can take much more heat/cold than that and still grow but it won't be optimally.
With that said, plants can be brought into extremem temps, say 15+ degrees and not die....provided it's not for any lenght of time. In other words, just because a plant was exposed to air at 15 degrees doesn't mean you've killed your plant.
For example, just yesterday a friend of mine transfered his plant from one house to another and the drive was 30 minutes. It was like 20 degrees and the plant is perfectly fine.
Many times I read posts with growers in a panic because something happened to their setup...such as the A/C shutting off accidently and the room his 105 degrees. As long as the plant has green still on it (not dried up dead leaves) it will make it. Same for the cold. If a plant is introduced to extreme tempuratures, it's ok...just as long as it's not for too long and the plant hasn't died.
In direct answer to your question, I have no idea how long it would take for your plant to show signs. Too many variables are missing such as the tempurature they're at and the lenght of time they're at that tempurature.
I hope this helps. If there is anything I can help you with, feel free to PM.
-EverythingHydro & Seemysig