Three to six months.... There's not a lot of hard, fast proof of the ideal time, but it's some time after the initial honeymoon phase of redeployment back with the family, as well as post-deployment leave, which lasts anywhere from four to eight weeks typically. That's why three to six months is generally what you aim for, because that's before the regiments get into their regular training routines, etc.
That seems to have worked reasonably well, but we rely on the chain of command to ensure that the members actually do go through the enhanced post-deployment screening. Part of the reason the third location decompression is effective is because you have a captive population. They're not going to simply go home as opposed to sitting through some of the educational sessions, for example.