Just depends on what you are meaning? If it is to flush water out the lines and get the RV antifreeze out. Sure, I would just before you leave out. Some people put water purification tablets in the fresh water tank to help freshen everything. I don't because nothing is in my tank. When I flush the lines, I always turn the water heater bypass back on and fill tank and flush the hot lines as well until all scale deposits and everything comes out clear.
I also turn on the propane and light the stove to clean out the propane lines with fresh gas. this seems to help the refrig. gas to work better and inside heater if needed on the first trip.
This process is usually takes about 30 minutes to do everything by the time I open the outside shower run clear and inside shower/comode is clear. I usually do it the day before I leave out wit assurance that there is no leaks from where I took the annode rod out for the fall/winterization or any other leaks around the 12 volt water pump or some kind of water line troubles that developed while in storage. My specialty tools would be at home if I waited to get to campground to un- winterize and found a problem.