Well, one example is that if you give Claire a massage at 21:00 she goes straight to bed and the game then will not give you the mom/aunt eavesdrop choice at 22:00. You must deliberately NOT give her a massage some night to be able to get this event at 22:00. I don't recall if there is a phone hint telling you to eavesdrop on mom at 22:00, but even if there is one you can't if she zonks out after a massage.
Yes, but if you do the same thing every day, you would never discover all of the events...
For instance if you watch a romantic movie every night with Ashley, she will never stay with you at night.
And if you never visit the gym in the afternoon you won't meet Veronica.
There are a lot of examples like that, but to me, that's part of the gameplay.
For that specific reason the game stops giving you stat points at a certain point, encouraging you to try new approaches.
Then again, difficulty level vs (fun) gameplay is a very subjective topic.
I try to look at it on a case by case basis, for example the cup of coffee that starts the event for Veronica was very tricky for a lot of players, so I added a dialog to help the player (before the implementation of the hint system).
If I see the same question several times, I adjust the game accordingly.
In the end it's all about finding the balance between effort and reward.