Can my veterans' disability rating increase or decrease?

Yes.  Unless the verterans administration (VA) specifically states that the ratings decision assigned to you is a permanent and total rating, it can increase or decrease.  The VA may periodically call you for examinations to determine if your disability has changed.  It is important to know that failure to meet these examination requests, can result in a reduced rating. 
Jim Keller
Senior Partner at Keller & Keller Law Firm