I use my memory, easiest way to sift through the pile of mediocre VN's that I've played. If I remember the VN its simply that good, and will regularly check updates for it
depends on the game, if it is a powerful story driven game, with a thoughtful well crafted mini-game, then absolutely, it adds to the immersion. but most games add it just to increase perceived game-time when there isnt a lot of content.
TLDR. Fap game= no mini game, story game= yes
implied adds to taboo of the game, such as cheating or incest. But for me it is a challenging wank when it comes to pregnant woman especially if they're in their third trimester.