When working on large projects, you may notice significant performance issues with your Revit model. Whether this will be long loading / saving times or trouble navigating and viewing your model. At one point or another I think we have all experienced these issues and it can be a massive drain on your time if you do not deal with the issues and take steps to prevent such problems. As a general rule, your Revit model should not be above 300MB in size for large projects, unless you have a 'Super computer' you will probably notice your Revit slowing down significantly when your file becomes anywhere above 150MB.