Has a whole year passed since I built this?!
It's not my intention to keep adding to this thread, but at the time there were several valid questions around the longevity of a baseboard made out of cardboard (and not exactly top quality cardboard at that). For the past 12 months the layout has been kept in the roof of my garage:
As you can see, it's been kept out of the rain, but the gap across the top of the garage doors shows that the wind, humidity and temperature can all get at it.
Actual damage to the layout consists of some of the backscene needing a bit of re-gluing, and the road developing a bit of ridge half way down.
Structural integrity of the layout? Well, here we go:
Bit of a sag in the middle, but I suspect it would have done that even when it had just been built! No doubt the track is helping to keep the thing ridged, but overall it's lasted well.