In September, we had a vacation in Switzerland, followed by a couple nights in Chamonix, then a week in Provence. It was a trip with friends. After our week in Provence, the airport we'd be flying home to was O'Hare. Our original plan had been to book a Delta/Air France flight from Marseille to Chicago. It's not a direct flight of course. There's a plane change at CDG in Paris. The daily non-stop from CDG to O'Hare is at 1:30 p.m. and that's the flight we wanted to be on, i.e., one stop to get home instead of two. But it sounded like an awful travel day. We would need to be on a very early flight out of Marseille to make the connection. We could have done it. But it would have involved getting up extremely early in the morning, like 4 a.m., driving an hour to Marseille, getting our rental car returned, checking into our flight and then waiting for it to depart, and we knew that any flight delay out of Marseille would run the risk of a missed connection. Even there was no delay, we still had the stress of having to make a connection, not knowing how busy CDG might be that day.
Instead of proceeding with that plan, we added one day to our trip and switched our rental car return to be the Avignon train station instead of the Marseille airport. After we checked out of our Provence rental home, we made an easy 45 minute drive to the Avignon train station, returned the car, and used pre-purchased train tickets to go all the way into the city of Paris (not the airport). We were going to be arriving in Paris at 1:40 p.m. or so, and with our flight home not until 1:30 the next day, we had rejected the idea of staying in an airport-area hotel. We had booked a stay in a hotel in the 6th arrondissement. The train took us to Gare Lyon, and from there it cost 10 Euro to take a cab to the hotel. We had a lovely afternoon walking the streets of Paris, followed by a wonderful dinner on Le Calief, a dinner cruise down the Seine (a particularly well done one!) That final night in Paris, enjoying the views on both banks of the Seine as we ate dinner, was the perfect way to cap off our trip. The next morning there was time to get breakfast at a cafe in the neighborhood, and pop into Luxembourg Gardens for a bit of a walk, and then we took a cab to the airport for our non-stop flight home. The cab fare was 60 Euro. We had so much spare time at the airport that we could have stayed in Paris longer, but we couldn't have known that and hadn't wanted to cut it close.
The CDG-ORD flight plus train ticket from Avignon to Paris cost less than what we'd have spent to fly MRS-ORD. The hotel we found in the 6th arrondissement was only 155 Euro, Hotel Des Grands Balcons. The rooms were small but the hotel was clean, friendly and very well located.
I'm not sure about this, but I think the rule that train tickets booked online in advance can only be used for that particular departure is no longer the rule, and you can change the departure time, maybe paying a small change fee. But if you choose your departure time carefully, you should't have to worry about that.