Eldgernon - RESPECT!!! I often have similar ideas throughout the tournament. It's a pity that you got so carried away and heated up that you didn't have enough time to complete even 3 days. Maybe that's the minimum? I hope your mind has calmed down now, or are you still daydreaming? ;)
Moreover, you need to take the absolute minimum number of days, even if at first glance it seems that it may not be possible to complete the map in this number of days, or it will only be possible under certain conditions that cannot be immediately predicted (whether it will be possible to destroy certain neutrals, whether the hero will receive a certain combination of skills)...
At the same time, you can immediately assess the minimum number of days (taking into account movement bonuses and spells) that you need to run directly in the worst case to the farthest castle. This number of days, as a rule, will be the minimum.