LOL, this is a funny ass subject.
First off, it's subjective in that where is this 1/4" filler and over how large an area? If you were doing some mashed up tight metal like at the end of a quarter around the tail light and you pulled a zillion pulls and hit everything up from the back and you had this mashed metal basically back into the shape of a quarter panel and tail light mounting and you needed up with a 1/4" here and there in small areas that you couldn't get to for what ever reason, that really isn't a big deal. If the metal was prepped properly, if the filler was mixed and applied properly, this isn't a big deal. That filler will last a life time, we will be dead and gone and it will still be there under the paint, no one the wiser.
But let's look at a different repair, a roof or hood with some vicious dents with stretched metal where the 1/4" bondo is covering three or four square feet, that is a whole different story!
On the extreme, I will forever have an example. From when I was 16, when I chopped the top on my truck, we are talking the thickest filler I have ever seen.
I had no idea what I was doing when I gas welded across the roof and warped it horribly bad. I didn't know how to fix it and simply bondoed over it. I put two gallons of Ditzler 999 (yes that was the part number) before I even sanded it!
I checked it years later with a large C clamp vice grip out to the middle of the thickest part, it was an inch and a half thick!
It did crack, long cracks up on the top, but no one was the wiser, just looking at the truck it looked pretty good.
Brian