Honestly not very often. Once I'm done with a game, I'm done. I rarely, if ever go back to it to revisit my favorite scenes. It just doesn't feel as impactful going back to them as it was in the moment, and it loses its appeal.
There are a few games that I go back to, either for the story or for the art. I mostly go back for the story line. But it only happens maybe a couple times a year where I revisit a game
Rarely, The games don't have a gallery or they have a fake gallery that is just bonus images, not the sex scenes it's so annoying. There are a lot of games I would love to have a gallery for, but they don't.
I never do it just for the sake of seeing the scenes, but I still think it's a most have feature for when I need to remind myself what happened since last update.
I have never once done this, lol. When I finish a game, I archive or delete it depending on if I liked it. If I liked it enough to archive it and I want to see the scenes again, I replay the entire game. If I deleted it, then there were probably no scenes memorable enough to go back and watch.