I brewed in 12th August. First tasted the off-flavor at kegging 10 days later. I didn't recall it until I went back to the notes, but I did detect it in both halves originally, but not as bad in the hop blend batch. 1 week later I tasted both batches again, no aspirin detected anymore in the hop blend half, and put that half in the fridge on tap. The Calypso sat until October 12th before tapping again. My notes show that I still tasted it distinctly on the 13th when having my first chilled sample. On the 14th is was already decreasing. Re-visiting my notes for both batches, I believe it may have been grain based astringency which settled quicker in the first batch and was all pitched with the first yeasty pull from the keg. The Calypso batch could have been roused more when putting in the fridge and thus didn't get purged on the first glass only a day later.
My guess is that if its astringency from grains, then it will settle out. If it's a mineral or chemical issue, then it may stay in solution. Time will tell.
My father says, "hobbies are supposed to cost money".