It really sounds like he is having problems letting go and dealing with his loss effectively. All these trips have to be having an impact on his life. It's possible he's keeping it at a healthy level, but ritual behavior as a coping mechanism for grief is rarely healthy.
I figure it’s the same thing as anyone else’s tradition of regularly visiting and leaving flowers at a grave, just more of a “bro” version. Graveyards are for the living, after all - the dead couldn’t care less.
Yeah, annual trips are one thing, and if it hasn’t been super long it’s fine, but part of healing is not needing to do such things anymore. It still hurts, but you move on