i dont move my trailer around much, but when i do i try to have it empty as much as possible.
Like mentioned the whole point of having a F/W tank is to be able to pack in the water you need for your camping trip. if you had to fill it while youre there you may as well not even have a tank. That being said, i dont think alot of the setups are designed to have the fresh water filled for long distance travelling, rather to travel 'dry' till you hit the last place you can fill it, and go from there with a full tank.
With 150gal F/W tank, that really cuts into my cargo capacity (thats 1200lbs of water), so travel is usually done with an empty tank till the absolute last place to fill up, and with such a large tank i fill it to the top, i would rather have it heavy than driving around with 75gal (600lbs) sloshing around!
'14 XLR 395AMP
'16 Ram 3500 DRW, 6.7 cummins w/aisin trans and 4.10 gears