I look at it from a perspective where the game is already build and ready to be played.
When you load your game,you don't load every map,you load each map separately,so the memory consumed wouldn't be added on top of the memory used for the previous map.It's like going from the start again,just a different map.Plus the build game contains the maps into multiple files,not just one.
My guess is this logic goes for the building process as well.
So to make a long story short,I don't think it will crash.

PC Specs:Windows 7 Ultimate 64-bit,Intel Core i7 960 @ 3.20GHz,NVIDIA GeForce GTX 480,12GB RAM,2x Western Digital 997GB HDD