This one is very hard to nail down since each VISN has some leeway in times from notification to submission of documents for appeal. The local appeal is usually (but not always) 30 days, and the VISN appeal has varied from 7 days to 180 days. The variance is very wide and should be noted on your denial, reduction, or revocation letter (in some cases like El Paso, no days are mentioned). The response can take from 30-45 days from VA and enlist a VSO if record omissions are possible.