I think that iodine test will be false positive in wort with unconvertable malt (like crystal and carapils).
I think that many brewers are using bad iodine solution, which in my experience varies in its ability to detect starch.
I recently switched to a new solution and it was positive after an hour. and after 90 min, and so on, until I gave up at 3 hours and just finished the brew session. I did NOT cook my mash enzymes either. I think it was positive because the iodine solution (Mucho Expensivo) was high quality discarded based on expiry dates from work and I took home to brewery therefore. When I compared to crapola solution I had that was years old it was negative when the HQ stuff was insanely positive.
Bottom line for me, I am going to mash for an hour, maybe more if its a really really light style beer at a low mash temp, or if I am doing a step mash. I am going to do an iodine test. I am not sure how I will modify the mash schedule as of yet, since I have this new very sensitive iodine solution, its causing me to re-think my process. Besides, an hour mash gives more time to clean the fermenters, and Relax and Have A HomeBrew too!