AbaKayDabra

Can someone point me to a place that would explain the process of these menus "timing out". What I have experienced is that some of these llDialogs wait almost indefinatly for a button click and other seem to only be active for about 15 seconds. I assume it has something to do with the corresponding listener event but I'm having a mental block on understanding it. For instance I have an emote hud that I want to pop up a llDialog box to pick a facial emotion. I would like the llDialog box to remain indefinatly so a second button could be pressed to start a different facial emote even if it is 5 min. later. Is this possible?