This depends on the specifics of the case and what type of review process has been chosen.
Here are rough estimates of how long it will take to process claims:
Higher-Level Review: 4-5 months
Supplemental Claim: 4-5 months
Judicial Review: 1 year (or longer with new evidence or a hearing)
Under the old VA appeals process, it typically took 12-18 months to review a new appeal and make a decision on it. It can take even longer in some cases.
For example, after a mesothelioma diagnosis in the mid-2000s, a veteran applied for VA disability benefits but never received them. His widow couldn’t successfully appeal until 2010 — more than five years after the veteran passed away.