That is my bad, Peter. Sepracor did a 6 month study with Lunesta. Here is a summary reference:
Data from a landmark, long-term (six-month), double-blind, placebo-controlled safety and efficacy study in 788 patients were reviewed by the FDA as part of the NDA submission for eszopiclone and served as a basis for the FDA's decision to not limit LUNESTA's indication to short-term use. Sepracor's six-month study was the first of its kind for a prescription non-benzodiazepine for the treatment of insomnia. The results of this study were published in the November 2003 issue of the journal SLEEP
I guess that is why an analyst asked MRK whether they were to do a head to head chronic study. The answer to that question led me to believe otherwise. I should have looked at the respective labels.
I do not know about Ambien CR, as I do not take these drugs since I have no problem falling asleep, even after a double expresso!