Just changed my RO membrane. How long until it makes good water?

[RicGio]

The PPM out of my RO was getting high (4-5 ish). I had a spare so I changed out the membrane. Initially the TDS spiked to 75 ,after running it for an hour the TDS had dropped to 3-4. How long until it gets down to the normal 1-2 I was running?

[raddogz]

I know if you normally change out the pre-filter and carbon block(s) you typically need to make at least five gallons of ro water before it "settles out"