So far, when backpacking a long distance from home, I've used my car. (I take my dog with me and don't want to trust him to airlines!) I always make a motel reservation for the night I come out. One time I came out a day early, but I camped at the trailhead (it was after sunset), slept late the next morning and still used the motel reservation (the motel was 4 hours from the trailhead). Of course when driving, I leave clean clothes in the car, so I don't need to do laundry until I get home.
If I were flying home, I'd make the reservation but plan one or two days' cushion at the end of the trip. You will definitely want to take a good shower (maybe more than one!) and launder your clothes before getting on the plane. I would also want to find a place near the far end of the trip to leave at least a sturdy duffel bag to protect my pack. Either that, or plan to buy one before heading for the airport. It might be that the hotel/motel you stay at when you come out will allow you to send ahead a piece of luggage for the pack plus a change of clothes and store it for you. It would be worth investigating.
By the time I've used up a week's food, my pack is small enough that it definitely would qualify as a carry-on. Of course I'd still have to check my knife and my trekking poles, and maybe the tent stakes. With most airlines now charging for checked baggage, it would probably be simpler to ship those items home.
After last summer, when I had to abort a trip in Wyoming's Wind Rivers due to my dog's getting sick, I plan a couple of "zero" days for each long trip and save one until the end. This allows for unexpected layovers, such as a barfing dog, a snowstorm (I'd have had that too if I hadn't aborted the hike) or blisters. By saving a "zero" day to the end I have the choice of taking it the next to last day or coming out early. If nothing goes wrong, the "zero" days give me extra time for side trips.