The conclusion i came to after reading a lot of posts, is that you should take the extender off at least every 60 minutes to restore circulation. I personally aim for 40 minutes at a time. Until recently I would take a 5-10min break between sets, but now i do 40min extending and 20min break, this way i can do 4 hours of extending in 6 hours and its not as uncomfortable.
My glans become pretty cold after 10-15 minutes, I suppose your do too? Opinions differ, some people say you can get nerve damage if your glans get cold, some say thats only if they start getting purple/blue.
How long have you been extending total and how often did you actually take breaks?
I had some tingling before but nothing that lasted for more than a few minutes, i suggest you take a break from PE for a few days/weeks .