Although four years is the longest we've heard of, the Knight foundations reports:
"Iraq and Afghanistan veterans filing a disability claim in Northern California have to wait 320 days for a ruling, according to a local congressman. That’s a backlog of a nearly a year for veterans seeking help for the back pain, post traumatic stress disorder, ear ringing and other conditions suffered through service.
While the problem is particularly acute in California, veterans across the United States have shockingly long waits for a variety of Veterans Affairs (VA) services, including mental health care – with 51 percent of veterans seeking help having to wait 50 days on average for a full evaluation."