Yes, you have to account for this in your code, and auto-rebuild them when they die.
If you check the documentation, you can see that you can check how long a creep has to live by checking the value of Game.creeps["JimmysCreepName"].ticksToLive
Hope that helps!

I did realise that - and it's a fairly easy fix.

Option 1: Leaving a map switches places with a creep in a position that would "block" a border.

Option 2: Moving from edge -1 to edge moves maps, new units appear on the edge.
Example:
Say you are on the edge at (1, 1) - the act of moving to (0,1) moves you to the next map, and you will appear on (49, 0) on the next map - which makes the edges of the maps unwalkable unless you're coming from a different map, any movement that would result in an edge square moves you to the next map.

Other work arounds that are better then the current system are also available - but that's just my opinion

Yeah, Vertigan, I agree completely, that would also be a good compromise.

Rather then having this odd system where you stand on a border and get alternated between maps each tick, why can't we have a system where if you use creep.move(LEFT) on the left-most edge of a map, you move to the other map?
It can't be too cpu intensive to check if a unit is in the destination spot before allowing a valid move - at least no more intensive then a normal check. The current system is pretty difficult to work with, and requires strange workarounds, due to the combination of the switching mechanic and the fatigue system.

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I've experienced the same thing, no idea on how to fix it. I get a similar problem running it at x2.

Errors in simulation mode are at times vague, and at others completely meaningless.
For example, an error telling me "Cannot read property 'pos' of undefined" doesn't help me at all if it doesn't tell me where the error is.
Inside the game on the other hand, this problem doesn't exist, as the error messages are a lot more informative. I was wondering if you could "update" the simulation mode to have the same error message information as the /live/ game.

in addition, in simulation mode room control level doesn't work correctly. It is possible to place roads at room level 1.