This answer is different for everyone. This is impossible to give a set value. How you practice will determine your rate of progress and when anything may “click”.
All my students who have been stuck at getting faster begin seeing immediate results when they do metronome work the way I built my speed. Most of us have to gradually build the speed up the same way you build strength. Slowly increase the tempo just like you slowly add weight.
There seems to be a stigma in the guitar community that any tension whatsoever is the worst thing in the world. If you experience muscle tension, you’re fine. You don’t get stronger by avoiding tension. Your muscles tire and tense up, slow down after a lot of use. This is normal and part of the process to pushing your speed barriers.
Joint pains, stuff that feels like a twinge, sharpness, etc. is different. That stuff is a sign to take a break and rest a bit. Muscle pain, where it just feels like your hand/arm wants to cramp up because you’re pushing yourself if fine. Your body WILL adapt to it. Eventually, the tension you feel will become less and less frequent, and eventually go away completely until you begin pushing your physical limitations once again.
And, as far stopping as soon as any pain sets in when playing guitar, for those that preach this, did they forget what it’s like to build callouses? Remember how painful it was for your thumb when learning barre chords? Pain is not necessarily a bad thing. It’s usually a good thing. Your body is adapting to the new stresses you’re putting on it, and will become better and stronger.
Joint pain is no joke though. Don’t push that stuff. Muscle pain? You’re fine. I have yet to hear of anyone tearing a biceps playing guitar.