It's not really a question of size, but of the amount of data that you are working with and how much information you want to present in each drawing.
The biggest problem that I have had is that the project starts out with say, a large surface from Lidar data, but you aren't displaying any of it so the program is fairly speedy. As more alignments, profiles and other design information is added the program starts to bog down. At some point you decide to turn on the surface contours - with smoothing, and you get "Fatal Error. Out of memory" Now you have to split up the project into multiple drawings, using Vault or data references to bring only what you need back into the current sheet.
Steve
Expert Elite Alumnus