You get to bring it up as long as it bothers you. He gets to decide how long he wants to engage on it. He cheated, you get to talk about how you feel insecure. This is the mess he created and here's the fallout. Tell him exactly the above. This is never in the past until one day it just is. With any sort of trauma - and this is a trauma - it will come up in random ways on random days because something digs at it. Again, this is the choice he made. Part of doing the work is understanding that it will have to be worked through at different times. We'd all like forgiveness and then never mentioning it again, but that's not how it works. Is the relationship important enough to work through this? He has to decide too.