That's intentional design, to keep the player actively running things and using up those resources. Otherwise you'd just log in once a month to do a little bit and move on to the next thing.
Totally obsessed with this game. I made a kongregate account just so I could save my progress fully. I do wish that when you go idle that you could automatically continue the dates. Like it would just keep hitting the restart date button when you were offline. Cause I know 15min date isn't much but I got a "I need 45 Zesty Fiestas" and I just napped instead cause that was way too much clicking time devoted. Even if I had to keep the game running to auto refresh the dates I would.
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That's intentional design, to keep the player actively running things and using up those resources. Otherwise you'd just log in once a month to do a little bit and move on to the next thing.