I'm thinking of finally tying all the locations in my campaign together with an overall hexmap, instead of fudging it like I have been. (keeping PCs on planned roads). I'm looking at changing the pathfinder hex scale from 12 miles corner to corner to 14 miles corner to corner. my reasons explained by someone else.
This would add about 35 square miles to each hex, from 93.5 miles to 127.3 miles. How should I change hex exploration time?
The realism for the exploration charts is already pretty much nonexistent. Exploring 93 square miles thoroughly enough to find non-obvious details like a singular radish patch, or a temple hidden in a forest should honestly take much longer than a couple days. For comparison:
GTA III land area: 3 square miles
GTA Vice City: 13.6 square miles
Elder Scrolls Oblivion: 16 square miles
World of Warcraft (Kalimdor + 2 eastern continents): 80 square miles
Bear in mind, the usual 'jogging' speed in those games is around 15 miles an hour, which is faster than professional marathoners. Even on horses, a party in pathfinder is only exploring at 5 miles an hour, and many parties are going to be on foot with someone weighed down by encumbrence or heavy armor, dropping the speed to 2 mph.
So, imagine how long it would take to see every corner of the orginial WoW, then multiply that by 3, or by 7.5. At MMORPG running speed that would probably take a few days (at 8 hours a day), which would mean well over a week, probably closer to a month, at Pathfinder speed. That's to cover less than one original hex in Kingmaker.
Hexcrawling is fun, but the time scales involved are already so massively fudged that another 35% doesn't really make things that much worse.
I crunched a few numbers (first to reverse engineer an approximation of exploration times, and then to work out times for the larger hexes the OP proposes). In almost all cases, the answers are largely the same as those presented in UCam. The effect is magnified in slower terrain types, but not by enough to really matter.
I'd just stick with the times presented in UCam, rather than re-writing the tables.
I agree that the exploration time will be negligibly impacted by adding an additional 35 square miles to the hex. However, the most important thing is for you and your players to have fun. If adjusting the table to bring exploration times in line with the new size of the area is fun for you and gives you a sense of accomplishment as your players explore your completely unique mechanics, I say go for it. If you would rather spend your time developing interesting and unique encounters within the hex as opposed to redesigning exploration speeds, do that instead. So long as both you and your players are having fun and it isn't hurting anyone, do what ye will.