It doesn’t make sense for their to be such a rule. How could a priest drag a person into the confessional because he is required to hear confessions for a certain amount of time? Priests in parish settings should definately make confession times generous for the sake of their parishioners, but we can always seek out confession. I was amazed to see people pull aside the priest we were travelling with recently and have their confessions heard in quiet corners of hotels, airports, public parks, etc!