It's definitely a risk. I'm willing to give it a go with the understanding that it might not work. If I have to go fallow again, so be it. But, to me it's worth a shot.
How frequently did you do WCs? I'm planning to do an initial WC 24-48hrs after the first dose (to remove the dead algae and nutrients), followed by 20% each week with the commensurate amount of CP added to the new water. My thinking is that this will keep the concentration high enough over time.
Every week and a half I did a water change. I left my skimmer off. In the 4 week period, I did about 3 water changes. By the third week you will see it start to degrade, I dosed a bit heavily after that. The very first week there was a bunch of crap floating around, but ammonia stayed down so I wasn't too concerned.