Will Extended Cooking Times Hurt Potency?

I made a batch of brownies yesterday using a store box mix
Added the 2/3 c of (canna) oil per directions
the box said to cook at 350 for about 35-40 min. I didn't want to cook at that high a temp, so I cooked them at 250 for about an hour or so.
The center of the batch ended up gooey and hard to handle. I'm sure I could have made it more firm had I cooked it longer but was concerned about the long cooking time.
Do you think it would have not effected the potency if I had cooked the batch for another 20 min or so

I generally as a rule under cook my medibles.. I like a good undercooked cookie as Tosh.0 says

gioua said:

I generally as a rule under cook my medibles.. I like a good undercooked cookie as Tosh.0 says

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OK... so what's the secret to having them cook completly? use a bigger pan so the mix is thinner?

well I can tell you how I do it since it's a bit odder then most..

I make the cookie mix like normal (use the prepacked betty crocker or whatever) I add the mix the ingrediants + decarbed pot dry sifted in.. the cook times call for 8-12 mins I usually stop em at 10 when you can see the edges or sides start to darken up a bit I remove them then since the pot was dry sifted in it will take alot of the moisture out.. I do the same thing or very sim when using canna oil=butter.. cook them as direceted but just pull em out or turn off the oven let them finish up in there for another 5 mns with the oven off

thanks for the reply gioua. when I have made cookies they have always turned out fine. I guess it's when you making something in a big batch (like brownies or cake) that I have a problem
I would like to cook them for as little as possible just to be safe

you are safer then you think you are when cooking at temps at 275-300 the pot is going to be wet so it wont burn unless you dont watch it.,., I have been medicated several times but I have a few timers around the house I always use too..