It's a major mess up.
Simply put, if I manage to total about 80 affection points on the last day of a 5 day event, then I would consider spending Cobans on extra combativity to get the girl before the event is over. (for an 11 day event, I'd want a bit higher amount of affection points, since I've already spent more combativity on reaching that, and 80 points on an 11 day event would mean I got less than 10 points a day, so less than 10 affection points for 50-72 points of combativity!)
If it turns out I have way less affection points than that, then I'll simply consider it not worth the effort, so I won't spend Cobans on extra combativity, and am even less likely to spend Nutaku Gold to get Cobans to aquire extra combativity.
I actually wonder whether the developers investigated any time in working out the mathematical probabilities in this game. Just drawing a couple of bell curves using the games' formulas and watching where things end up could be an eye-opener.