all the steel is on the hone and only the spine is left...
but seriously... depending on the metal, the edge could become too thin and be less than ideal for shaving for a myriad of reasons. it's a trial and error type judgment...
I'm not sure what you mean by "limit of honing." Once the razor is sharp enough to shave without pulling, it is honed as much as it needs to be. Experience and practice will allow you to determine this point without relying on test shaves.
There's getting the most from your stone, as you get closer to the limit the bevel will feel different on the stone, some stones kinda suck the razor down onto it.
I don't think anyone's found the limit of honing, edges are still holding up with 0.0125 micron abrasives and I've not noticed any issues if I hone the blade with a finishing stone prior to every shave for a few weeks.
i quit chasing that edge...... because i found when i got wayyyyyyyyyyyyyy out there with trying to get the "ninnnth" degree out of it the edges were harsh and unforgiving and just plain unfun to shave with... *(i am talking edges with oil and ultra fine diamonds and a hour spent just on the finishing stone)...
NOW.... i set my bevel... i use the coti to bring it up to popping hair floating above my leg or arm... then either finish on the coti with oil.... or progress to one of my other finishers with oil......
takes much less time ... i have fewer scars on my face... and the shave quality is 100% better... i can now concentrate on shaving my face and less on unscheduled massive exfoliation...
my ratio of BBS or EFDFS *(extra fine damn fine shave.. which is almost bbs but the tinyist bit of scritch by my adams apple) as opposed to just a DFS is extremely high now...
Everyone is chasing the best edge, but sharpening usually ends if you reach a comfortable shaving edge. Better edges will come with more experience, and better technique, and a lot of patience