The only reason we still have a bike is because my wife won't let me sell it. I think it's more about the number of hours that can be ridden than the number of miles. My wife and I can comfortably do a 9 hour trip, zero issues. We stop every hour for breaks though. The most miles we've done in one day is 371. We could have logged more miles, but we were at our destination.
The bike has become our little getaway device, so it's outfitted accordingly. Corbin seat w/backrest,Throttlemeisters, a huge tankbag and we upgraded to Corbin hardbags. We did a 5 day trip but overpacked and had to use a backpack (I like a pair of running shoes and I wear sz 15) she tried carrying it and that lasted around the block. We will likely do a similar trip this year as well and will just pack MUCH lighter.