In many ways I wish the first thread ever here about thrombosis had never appeared.
A thrombosed vein in the penis is a rare event. One is characterized by noticeable heat to the touch of a hand or a finger, pain, usually some obvious discoloration, and swelling in the vein and in the tissue surrounding it.
There is a lot of concern here at Thunder’s about veins. Without them (and arteries) you couldn’t get an erection. Without them, in fact, your cock would wither and fall off with no blood supply.
So when penile vascular vessels become more apparent on the shaft surface, as they will when you do PE, try to go with that. If no pain or discomfort, it just means that you are building the blood supply potential to your unit. You are only increasing your erectile function and just possibly, your partner(s) will be more impressed when they look at that nastier-appearing tool.