I used the performance evaluation tool to see which components in my top level assembly are taking the longest time to open and surprisingly many of the components that take the longest are very simple parts such as bolts and nuts. These bolts and nuts files are all updated to the version of Solidworks I am using and they have had the thread detail taken out in the model. I'm stumped as to why these components are taking so long which is affecting the open time of the assembly. Many of them take up to 0.5 seconds to open when other much more complicated parts take less than 0.01 seconds to open. 

Does anyone have any tips or suggestions on how to decrease open time for parts?