Hi Marty, I want all of the frames in my brood box to consist of mainly worker comb. All greater than 80-90% worker comb. That way I’ll get a good population of worker bees. If the bees got a chance to completely finish the frame they messed up, there would have only been about 30% of that frame available for the queen to lay fertile eggs in. The rest of that frame would have consisted of drone comb & gaps.
If the bees build a beautiful frame of worker comb, as long as that frame remains like that, I see no point in changing it. It’s when the bees start making holes in it & replacing them with drone comb etc., that’s when I’ll replace them.
As @Dee said, when you can no longer see through them is a good rule of thumb. However even if that frame maintained it’s original high percentage of worker comb, it is still a hygienic frame because each cell is cleaned & polished between each hatching.
When we use foundation, it’s usually a larger cell size than what the bees do in the wild, so there is lots of room for a cocoon buildup. Also the bees in the wild don’t have the luxury of having their combs replaced.