When can you first taste off flavors?

I have been fighting "astringency" for a long time, and today for the first time I think I might have won. I was wondering though when can you first detect astringency from the mash? Right away, or does something have to happen during fermentation to bring out flavors. Today I didn't detect any off flavors in the wort, but when I started thinking about it, I'm not sure if I ever have. Anyone else have any experience w/this?

i taste before pitching and along the way...cant say i have had astringency issues though. What are you using as your mlt?

Im using a large rectangular cooler. not exactly sure of the capacity, but I've never had a problem.