Hi,
First of all , you can do the 4 buildings at one Revit file , no problem at all , but there is some points you have to take in considerations for taking the right discussion ...
* The level of detail of your project , as this will have a strong impact on the file size which will control if you can do all the 4 buildings at one file or you have to create each building on a file for better performance and better file size.
* The Sheet Production: do you have sheets that compile the 4 buildings?? or all the sheets is per building ..
- If all the sheets is per building then you better go for a file for each building.
* Coordinates:
if you use the multi-files for multi-buildings , then you have t think about the linking way (origin to origin / center to center / shared coordinates)
* the number of architects that will work over the project .
If there is an architect for each building (for example) , so it is much better to create each building in a file , and after that link all in one master site.
I think these points are the most important ones as a brain storming at the start up of any project , to manage successfully what you will do after that.
I wish I helped you 🙂