I would say that you should not poke acupuncture needles into it, but after 30-45 days it should not be a problem to massage it.
The only sensations after installation are the soreness that remains only until healing has begun (a few days at most), then occasional “pinches” and “itching” as nerves reconnect and repair around the implant. I think the “2 years” comment about “itching” is probably something I said about an itchy sensation coming on momentarily every once in a while for around 2 years or so after installation… but it’s more like the kind of itch you get on your arm, you scratch it once, and it’s gone… just a twinge that happens to occur directly overtop the implant (at least for me)… though I can say this only happened with my very first implant in my left hand I got in 2005… all the other implants I have did not have this “problem” so it might be installation-specific, meaning the conditions of that specific installation might cause a nerve that has healed around the implant to occasionally (a few times a year) trigger an itch response.
The NExT has two chips - NTAG216 and T5577 … the NTAG216 has lock bits as mentioned above and configuration bytes which are sensitive and could cause problems if accidentally messed with. We learned our lesson from the xNT and provide the NExT in a pre-programmed state with lock bits disabled and the configuration bytes pre-protected via AUTH0 byte and password feature.
The T5577 is still possible to “misconfigure” if a write process fails and tears the data being written, but with a proxmark3 you can almost always fix this problem.