If you can leave some extra space from the edge of the layout to the track it's always a good idea for those reasons mentioned above.
It's also good if your adding scenery to your layout.
Having said that. I have been running my trains at scale speeds for 15 years.
The few derailments I've had were operator induced, by things like bumping one train into another because I forgot a switch was thrown.
I modeled h.o. back in the 90s. There was always some random derailment for no apparent reason no matter how perfect track and switches were laid.
I've not experienced anything like that with fastrack and the turnouts are non derail so no issues there either
O Guage stuff just runs reliably, and that center rail helps prevent the herky jerky operation of smaller scales that require impeccably clean track.
