WE did the one-hour tour of Philly - it was a generous hour. More like an hour and 15 minutes, I think. Natalie was a great guide! I would request her, if they allow requests.
I should mention that these tours of Philly take you are out on the streets in and mingling with traffic. Some skittish people might not like being so close to the traffic.
Also, if you arrive early, there is a tiny coffee joint about two doors down from the Segway place and they had the best vegetarian bagel sandwich I've ever had.
Remember, for a good time, request Natalie!