There are lots of TV ads about legal firms offering to help veterans through the VA process, They charge a percentage of your gains for the rest of your life. All the VSOs, ( VFW, Amer. Legion, 40 & 8, DAV, MOPH, etc.) will agree that going through their trained service officers is the best way. All Veteran Service Organizations, chartered by congress, do not charge to help our brothers and sisters through the government maze. The VA has an annual budget of 3 billion dollars. Therefore, the maze is big and intimidating. The article address below was written by a legal firm seeking business.
But, perhaps this article also lists some VA rules about ratings and permeance of ratings by which the VA must play, that you did not know. https://www.thevaclaimslawyer.com/blog/the-55-year-rule-for-va-disability-ratings
................ We advocate contacting our trained, Chapter 8 Service Officer, who charges no fee. Our service officer administers our mission to help veterans in need of help. If you are in another state, or coming to our chapter is not possible, contact a VSO close to you and ask for their service officer. All states have some of the organizations mentioned above and it could mean money in your pocket ( for you and your family ). This chapter meets in Lansing, Michigan, See Officers on our home page for officer information. Our Sr Vice Commander is also our service officer.