I dislike the short-term recipes also. I can't do them at work and I can't let them go overnight, so it's a couple of recipes every evening. I have several stoves with one or two short-term recipes on them. I keep old stoves with 6 hr+ recipes to keep food on the counter.
15 day goals might be nice, but it seems having double the time requires more than double the parts so it's not that much different than week-long goals. I could use gems, but where's the fun in that? Although I might spend money on a game if I could sort neighbors, parts and appliances. Or select multiple neighbors to gift.
I didn't even try to complete this goal.