Hopefully at the beginning of the project you have defined which BIM use you want to service with this information model you are creating. So the performance of the project will be measured against the intended BIM use.
So no word about file size yet. Why do I care about file size. I use the file size of families and projects for a small part of Revit projects health checks. I take a look at file sizes when I open new projects and see how they handle. I have seen huge Revit files that work like a charm and small files that handle like a hung over sleepy turtle on a holiday. So file size for first impressions. So if I get big files that handle very well than that often is a first good sign that that company has got their model authoring well under control. It’s not a guarantee it’s just one of the metrics.
Next I like to save the file as a new project and purge them. This tends to give me an impression about file maintenance. Proper file maintenance is good for performance. See image below, an example of a set of files that nearly got halved in size by doing some basic maintenance.
Take a look at this post from Toms hardware: gigabit-ethernet-bandwidth. Every bit has to travel the network. Also be aware that unnecessary big linked files are being turned into even bigger temporary files when a project is loaded. Another performance hit.
When I do a health check I tend to start with the biggest files as statistically I am more likely to find issues. I write reports for companies where they could make improvements. (these improvements can be things like view performance, family content, model management, drawing production, model authoring or others)
I also save all the families out of the project and take a look at their size. There are guidelines about what sizes a good families should be. BUT if you know what you are doing feel free to ignore them. I tend to start with the biggest families first. Big does NOT mean bad. Big families just have a bigger chance of modelling oddities that need to be addressed. Or they have a bigger change of speed increases when improved.
To come back about my definition about performance. If the file handles super fast but it does not serve the intended BIM use than it’s performance is bad. If it serves the BIM use spot on but it handles slowly, it performs much better. Of course we all try to find the sweet spot where the handling is great and the BIM uses are being served.
To conclude file size can be interesting for some of us. But I advice you to focus on models that serve the intended BIM use.