TrueAchievements says 15-20 hrs. It took me 25 to get them all. HLTB agrees with this time for completionist.

Me too! I also highly recommend:

Gone Home - explore your old home to learn everyone’s secrets

they are definitely real animals and not people.

Nothing suspicious about that!

I was also going to say Brothers. There’s one moment (anyone who has played it probably knows what I’m talking about) that actually gave me a visceral reaction.