For length I don't feel that there's a need for a warmup, especially when the temperature around me is high (or when I wake up and my body is still warm from the blanket). For girth I think 5 minutes of a thorough warmup (rice sock) is enough, anything more is overkill...
ditto, I think warm ups (and cool downs!) have been essential to my gains. I do both length and girth on the same session so I'd say it's important for both.
In my opinion a warm up is vital for girth. Best to use a heat pack. Stretches don't warm me up for girth enough. The circulation is still too weak for the workout that ensues.
Yes warming up is always essential even if you live in a warm climate. I would recommend MOSRED and heating fans. MOSRED I prefer to use after a session for recovery and increasing collagen production.... (there are more benefits).
But what is important to remember that if you really heat up your tissue (getting the heat deep inside, also into your inner penis) before a session and keep it heated during the session.
You will experience more temporary elongation and expansion after and during the session.
Always remember: Temporary elongation and expansion will generate permanent gains with time.
Many say they live in a warm country so there is no need for warming up their tissue. I don't agree with this. Even in the middle of the summer at 30°C/86°F I needed to use my heating fans to get my tissue warm. There is nothing wrong with me. My belief is that a well heated tissue will generate faster gains.