How often do airlines change their international flight schedules?
 

For instance, US Airways for quite a while has had direct flights from Charlotte, NC to Frankfurt International which land around 10:30a.m., Frankfurt time. However looking ahead to our actual travel time in September, they only have arrival times around 6:30am.

Just wondering if airlines change their flights schedules often, or maybe add flights later if necessary?

Airlines change their schedules according to seasons;fuel prices;terrorist or government situations,return flights,etc.International flights are always in full swing in the summer but the shoulder seasons of spring and full are tapered down so don't expect for them to "add" some flights later.The airline marketing people have this down to a science!

Ugh. So I may need to seriously consider buying my tickets sooner than later? I need 8 of them, so waiting for a good sale might mean a better price but not enough seats?

(Plus lowering my expectations for getting an "ideal" flight.)

I work for a major US international airline and word around the company is that the oil is going up and so will ticket prices.You do realize that you are paying less for an airline ticket than you did 10 years ago?
If you need 8 seats and can start watching the major sites for the discount I would but realize that you will have to be vigilant about it.
As for international/European flights-most of them arrive in Europe from the states between 630am and 1000am to time for connections.

Don't buy a ticket this far in advance if the exact schedule is important to you. In fact, the flight could be canceled all together. Not that it's likely for CLT-FRA.

If you buy tickets a few months in advance, or earlier, it is almost certain that there will be changes, although often they are very minor.

Since you are flying as a group, it would be a good idea to buy the tickets as one purchase, then they will be linked together and the airline will try to avoid making a change for some of you and not the others.

I booked 3 flights to Athens using Continental miles in November for September flights. One from Reno and two from Newark. In 3.5 months I've had multiple changes on both routes. The flight back from Athens to Reno via Toronto on Air Canada was just cancelled so they put the passenger on the same flight the next day but the rest of the legs on United remained for the day before. I'm glad I checked and this is an important rule I've learned with buying well in advance.