I have a 42 gallon wheeled barker which is large enough to hold the capacity of my 40 gallon grey tanks. I don't use it often but it allows you to have options.
The option to stay without hook ups for weeks at a time if you like.
The option to choose state,county and COE parks when available vs. private parks. The option to use a W/E or just electric sites if that is all that is available. The option to escape FHU places and take advantage of more spacious and remote public parks. FHU site are very convenient however they can be very constraining as well. It's nice to escape and explore all the great places places that don't have sewers!
Motorized RV's may have the option to just pack up and drive to the dump station.But my 5 slide bunkhouse would be way too much of a pain to take to the dump station.
In general my family can go 3-4 days will no conservation before dumping. Using the blue tote once or twice during a trip for grey water is a nice option to have. THe Blue Tote is a nice option to have.