I don't have the room to accumulate and then mix large batches of water for water changes in either my office (175g) or my condo (400g).
With respect to the 175g in my office, I have a service do a 40g waterchange once a month (I do all the day-to-day stuff my self). Larger if I think it warrants it. I consider the money well spent since they haul in all the RO/DI water and equipment needed to do the change, and are in and out in a few hours.
With respect to the 400g, the tank is still new so I have not had to deal with water changes as of yet. I nevertheless will probably have the same service do a large (100-120g) water change ever couple of months to begin with, and then go from there.