Is it impossible to fully recover sleep debt?

I've read that there is a debate within the scientific community as to whether or not chronic sleep debt can ever be fully recovered. I've yet to read a long term study that has monitored a persons sleep habits and tested for sleep debt recovery that spans for longer than 3-4 weeks. In saying so, how is it that science is confident that chronic sleep debt recovery is an impossible task? if anyone has an answer to this, please provide references, or at least back your claim with scientific data. I don't want hocus pocus.