We usually keep everything short. If the other person can't talk, you should probably loosen up some and make sure there is some sort of safety "thing". Some sort of signal that works for what you do. Be it knocking on the headboard three times or a word, it needs to be simple enough that you can do it half way to passing out. You should always check the other person and make sure they aren't turning colors or anything of the sort. We like to keep things light and short so I don't know about more extended sessions, but this works for us.