Yes, try for more mileage toward the end of the trip, when hopefully you are stronger, and possibly you can leave some disposable items out of the load for the last day, such as a plastic ground sheet, excess food, and so on. My longest day ever with a camping load was on the last day of a mountainous trip--ended up riding an hour into the night, but made it. (Truckee to Sacramento, CA)

And plan on everything taking twice as long as you hope it was going to--lunch, fixing a flat, waiting for a companion to show up, climbing a mountain, etc. That's just the way it seems to go on a tour.