I think ultimatly warm up and warm down should be taken fairly seriously, anything that gets blood flowing down there is a good thing. I think its good for recovery and probably good for flacid gain too. I have been toying with the idea of doing a warm up on rest days aswell as i feel if you can keep the blood flowing down there at higher levels prehaps this can help maintain the temporary gains you have got with your work out. That said this is just a crazy theory of mine, however i do think they are a good thing. probably it depends on what you are doing, if you are doing strenuous stuff i think the warm up and down are very important and often i feel like i want the warm down just to relax things down there after them being tense. Its up to you though, i guess if you stretch in the shower then you might of kept some of the warmth there. Incidently i have read about people stretching in the shower, how do you do it? i alway get too wet and slippery to stretch.