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One trick I've got that works occasionally is the SLOW method. With either a 90degree allen key or a t-wrench (ie, something with some flex in it), put some easy torque on it and just hold it there. Kind of "bounce" the torque up and down. Be patient and stick with it. I've had them where I was working on it for over five minutes before they broke loose.
Or just plan b the bastards and drill off the heads.
Variation I use on nasties like caliper bolts is a socket allen with a breaker bar. Push in and keep inward pressure on the socket while pushing on the breaker till it feels like it'll almost want to roll out or break and just hold the pressure on bar steady, like you say may take a bit to let go but it will. Yet to have one not pop loose doing this and no damage to the bolt.
What finally worked: I heated the button head directly with a propane plumbers torch, (started smoking from the bolt), then drove a T40 torx impact socket into the 7/32 hex fitting, then smacked it several times with a $9 Harbor Freight impact driver.
It put up a hell of a fight!
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