Not that i dont like "Guess Who", the actual version has 119 images (dont know how many will be added) but afaik Yumiko sends you a message every third day, so even with "cheating" (save and reload when wrong) it takes about 360 days (or a few days more because you cant start it from day 1) to get all of them, i think even if playing slowly and with grinding you are finished with every event/scene/appointment earlier by far than that... and grinding only for the missing images is a bit boring i think...
Maybe Guess Who can trigger once every day when started, or maybe every third day until day 100 and then every day to make it possible to accomplish that earlier... Just an idea