If your tank doesnt have livestock in it, I wouldnt bother. Water changes replace trace elements and remove toxins more than anything else so I guess it depends where your tank is at since I know its pretty new. Your biggest worry would be salinity after 4 days of evaporation. I'd load the tank up to the brim with some RO before you go and get your salinity low (1.021) and allow evap over a few days to slowly bring it up in your absence.