It is highly unlikely that you could run non stop by doing this, unless you were just using your DI unit for cleaning your water and bypassing the RO.
In the past we have refilled midday using just the DI unit and providing the mains water is not too high to start with and your resin is in good condition you can get 000 - 005 readings, but your resin will be shot in no time.
Cost it out, it is often more cost effective to use an extra 1/3 bag more resin if you can get the work done in a day rather than going back twice.