Let's say you put 60 hours into each of them (which may or may not be generous depending on how you play).
It would take you 480 hours to beat all the English NISverse games you haven't beaten yet (all of them except Disgaea... and Rhapsody because ell oh ell Rhapsody).
If you spent an hour and twenty minutes playing every day, you could finish them all in a year. Since 60 hours is probably longer than it will take you for some of them, the actual amount of time you'd have to play every day is much less.
You can do this, GFK.
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Ace Detective in Sir Chris' Police
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