The iSee cloud drive can be a useful tool for storing files for loading onto iSee boards and for sharing files between participants.
The speed of the first opening of the iSee cloud drive depends on the speed of your network connection. The next time you open cloud drive in a session it will be instantaneous as the content is loaded from cache.
If you have a slow network connection and don't want to be impacted during class time, it may be a good idea to open the drive earlier at a less rushed time so that it is cached and opens faster when required during active teaching.
It is currently not possible to close the cloud drive while it is loading. This may cause an issue in class if students with slow network connections inadvertently click on the drive during other work. You can create a custom role for students to remove their access to the cloud drive if this is an ongoing issue and cloud drive is not used by students in your class. See here for creating custom session roles.