>>534657646
I read it about a year apart and I had no problems, but if you wait too long and you start to forget you'll probably run into trouble. It's honestly my biggest problem with the VN, the Chusingura FD is canon and all the events occur, but they didn't want to just replay the same scenes, so they skip over the scenes or show you what was happening elsewhere at the time, like there's a scene where Ken gets back to the base and they go "oh Ken, you just missed Suguha, he was here only a minute ago."
It's kind of a baffling decision because not including the scenes depicted in the Chusingura FD means it's a Shinsengumi VN where they almost completely skip Ikedaya (since that was in the Chusingura FD). It also means there's about five hours or so of the VN where half the main cast vanishes without explanation and when they come back they're badly injured and in Isarin's case, a radically different life philosophy, and when Ken asks what happened to change them all so much Hijirin just says "We got our asses kicked by 200 year old ghosts." I can't imagine trying to read Miburo without the Chusingura FD, it'd be incomprehensible.