I was curious, so decided to do some math on what it would take to ACTUALLY have coffee for life. 5 triple shot espressos will cover you an entire day. This turns out to:
560 triple shot espressos a year
1680 coffees a year
8400 coffee beans a year
Now, if you want your junimo huts to do the harvesting for you, you'll have to plant them on your main farm on the first day of spring, which will produce a minimum of 96 coffee beans per plant. 8400/96=87.5 coffee plants planted each year. Of course, you'll want some extra beans so you have something to plant next year, so call it 89 plants total.
(You could get buy with fewer plants if you put them in a greenhouse or on ginger island where they grow perpetually, but at that point you have to harvest them every 2 days manually and I think the time involved doing that almost definitely offsets the benefits you get from the coffee itself.)