Probably around two hours when I should've limited myself to one hour to avoid burning myself out. Talking to villagers and catching bugs and fish keep me playing. The worst offender that keeps me playing is completing the nook miles + achievements. Really, it's like giving me dopamine every time I complete one and keeps me going for a while.
I'm not working rn cuz of quarantine lol so probably 2-4 hours depending! I'm trying to read more and go for walks but there's just nothing to do except play NH these days haha
To me it feels like ~30 mins to an hour a day? I just recently took a week-long break though, and my average play-time is 4.9 hours a day so I'm not sure who I was when I first got this game