Longest I ever went was John Wayne to Portsmouth in 9.5 hours block with one fuel stop in Lincoln Nebraska if I remember right. That was a special situation that will probably never happen again, but it can really do some bladder busting legs.
99.9% of the time you can have an FBO dump the lav. I had to do it only once, but that one time had to be the time the guy crapped all over the lav.
Also had to pick up toenail clippings at a random airport with no FBO while we were waiting for a guy to go to a meeting and come back. Wouldn't have been bad if the vacuum wasn't broken.
Those 2 things are the only things that stick out as bad or gross and are complete outliers. It is a great place to fly