Presumably every player has an equal amount of time to exploit either an internal or external boundary. So, in that regard, as long as the rules are evenly applied to each person the game is fair. 10 seconds or twenty seconds, its up to each player to decide how to play in the world. Any player that rigidly respects a boundary, let's say never crosses one, could put himself a flanking disadvantage to other players. For an internal boundaries example, if one always walks around a walls one could be at disadvantage to another player that always jumps over them. Of course, jumping a wall is also jumping blind and may not always prevail. Equal chances to all.
Thinking about this a little further, I wonder, why not just change the game to have hard external boundaries? Then if a player runs into one (on foot or on a vehicle) they and just bounce off. They don't die, they just bounce off like a hockey puck, no timer, no death, just a new trajectory. Timer problem solved.
