The solution is simple. When it's about to "go away" display it again.
The simplest way to code that is to use set_task.
PHP Code:
public start_displaying(){
set_task(1.0, "display_msg", 2356, _, _, "b")
//function display_msg will be called every second
}
public display_msg(){
//this function will display hud message that lasts 1 second every time it's called
set_hudmessage(0, 255, 0, -1.0, 0.88, 0, 6.0, 1.0)
show_hudmessage(iPlayer, "Kills: %i", userKills[iPlayer])
}
There is something better than set_task described
here, but it's harder to use.