Yep, TC holding tanks are always a tradeoff between lots of capacity (and lots of weight) and smaller capacity (and less weight). Assuming the above adventurer's tanks are full, the combined weight of the contents would weigh 852 pounds! It's down low in the TC, but that's a lot of weight.
Our Lance has a very small capacity:
18 fresh
11 grey
12 black
We have ways of extending the days of the grey and black tank. Our showers are very short, usually at the same time sitting on the pot with your feet in yet another plastic tub to catch runoff. During hot weather (not our first choice) and way out there, we use the outside shower and a funky little shower enclosure that looks like a tall narrow pop up tent. Of course, none of this water finds its way into the grey tank. Our dishwater goes into a plastic tub (yes, the same one) and is deposited outside saving space in the grey water tank. We can honestly get about 5 days using this system, but we don't stay in one place very long. For us it's the journey, not the destination. If you like to quickly get to a boon dock destination and stay a couple weeks, obviously this style will NOT work for you.
We supplement the fresh with 6, gallon plastic bottles stored on the floor in a rearmost cupboard space. This we use for cooking and drinking. Another 24/16 oz. plastic bottles for drinking are stored in the dead space in front of the inner fender wells (through the little doors at floor level).
The truth is our model Lance was sold as compatible with a H.D. 1/2 ton pickup and they needed to shave every oz. of fat off the carcass to make that work.
Since this is our first camper we have just gotten used to a spartan and light weight existence on the road to XTC. YMMV.
regards, as always, jefe
'01.5 Dodge 2500 4x4, CTD, Qcab, SB, NV5600, 241HD, 4.10's, Dana 70/TruTrac; Dana 80/ TruTrac, Spintec hub conversion, H.D. susp, 315/75R16's on 7.5" and 10" wide steel wheels, Vulcan big line, Warn M15K winch '98 Lance Lite 165s, 8' 6" X-cab, 200w Solar