ahem..... i will get past my laziness and post what i know of the subject.

flashbacks are a reoccurance of a past experience hallucination, or strange happening from a psychadelic. I have never heard of any mushroom flashbacks and I highly doubt u will ever have one. the length of a flashback varies.

remember that many people shroom very often and most of them never have flashbacks, and I would guess above 90% don't. flashbacks are more often thought of when acid is brought up. just don't become a daily shroomer or even weekly if u are worried about flashbacks.

http://www.erowid.org/plants/mushrooms/mushrooms.shtml