While getting caught off-guard by a life check can be a pain in the ass, you only really have yourself to blame if the players puts a message in chat like anybody else would. It's just our own ignorance at the end of the day.
However I feel a minimum time requirement would be beneficial as it would deter people from using stupid times and it would make our lives easier should we have to punish people. For example, I've been told to get tested within five seconds or I'd be killed when I was on the other side of the map. It would allow people to actually use their brains and would (potentially) increase the chances of people noticing it before they are killed.
In my opinion, 30 seconds is a tad too much. 15-20 is decent. If you don't notice it in that time, then you really aren't paying attention.
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