Every woman is different which makes them a wonderful puzzle. For some their nipples are wired to the parts below, Other are too sensitive to play with. Evey time I am with a lady it is like trying to solve the puzzle as to which combination of stimulation will give her the most pleasure! I must admit the bigger and longer the orgasm the more I like it! Minding you that the journey to bliss is of equal importance!
On a side note, If you think cold make a cock shrink, try keeping it hard in a sauna or a very warm hot tub!
Simply put, when it is cold blood vessels contract so you can not get an erection, When it is hot you would think they expand but in reality ALL the vessels expand which is why you can not hold an erection, You need the vessels at the base to contract to hold the blood in the penis, The design was good, you need a warm shaft provided by the lady with a cool base. Your balls are a great cooling fin!
For the ladies it is just simple contraction of the skin and blood vessels with no place for the excess to go so they pop out.