In theory it sounds good but again no one has ever published anything that I am aware of that shows this to actually work. It can't hurt anything though and if it makes you feel good go for it. Russ is correct in that for it to do any good whatsoever it needs to be done at shutdown, you will see other recommendations to flush at start up (supposedly to reduce TDS creep but the TDS creep is already on the treated side not the waste side) or periodically during use but really the brine will be back at 120% to 125% of the tap TDS again in no time. I find it is far more beneficial to simply keep the waste ratio at the recommended 4:1 or in rare cases 3:1 or in extremely rare cases with softened water and way lower than normal TDS 2:1 so you get continual flushing and use the system at least every 10-14 days to keep it fresh. I also recommend installing a DI bypass valve such as Russ does on his Premium systems. Open the DI bypass on start up to flush the TDS creep out of the treated side and your DI will last much longer. This does have proven value. Everyone is on a "waste reduction" trip and while this is the "green" thing to do, all membranes must be flushed in order to last and work well. I always recommend anyone buying a RO or RO/DI system learn about their water conditions and tailor or fine tune their new system to fit those conditions. Many vendors still use the old fixed type flow restrictors and they are often not correct for conditions. We don't all have 60 psi, 77 degree water and 250 TDS so you may be wasting way too much or too little and either costing yourself money in water down the drain or in membranes when the waste is not sufficient. People like Russ and Spectrapure realize this and provide capillary tube flow restrictors the end user can trim with a razor blade to adjust the waste ratio once they install the system so it is perfect for their unique water conditions. They also try to educate their customers on how to test and troubleshoot their water and RO/DI systems so they get maximum component life and the best water quality. RO/DI is not just plug and play or set and forget, you need to spend a few minutes every so often to make sure it is performing as it should and in the end it will save you money and provide a better quality effluent. Simple things like testing the tap, RO only and final RO/DI TDS every month or so, monitoring the inline pressure gauge for signs of filter plugging or using a low range chlorine test kit to monitor for chlorine breakthru from an exhausted carbon or occasionally measuring the waste ratio since it can change with the seasons and water temperatures all pay off in the end.