Ive always been able to do it. I remember a group of us playing at school once, we were running around pissing on each other ( like you do).
Anyway, i could stop and then start again no problems. I was asked how i managed to do it.
I don't know, i think it may be a bit more effort now. Ive not tried for a long time, i may test it out next time i go, if i remember.