I think I got that solved for me! Actually the nerve cells themselves are in the brain, and these are the only critical part of the whole systems. Axons, which are responsible for the impulses, have the ability to regenerate, so there is no danger for permanent injuries from proper jelqing in my opinion. Basically our boides are resistent and are able to heal from way more serious injuries, such as burns, hits and even a cut part of your body could be sewed and successfully saved, so that the sensitivity is not lost, otherwise we would have been senseless creatures after couple of hits during childhood. This is of course not the case for brain/spinal injuries…
So I think that you can temporarily encounter some loss of sensitivity, but nothing critical in the long term, after a recovery break. To avoid even that, use a lot of lube and be gentle with your dick. I never felt pain after PE session and my sensitivity has always been good… Anyways could not say the same about rough sex for example. After 5+ cums with couple of hours spent fucking, especially with a condom on, my dick is super insensitive, but after 2-3 days it’s again okay. So I think there is nothing to worry about, but would love to hear the opinion and experience of some vets.