I use source control on every single Domino database that I work on. Often because I want a database under formal change control so that I can relate individual change requests to the changes made in the source code. But also mainly to cover my backside. When I make a mistake (and it is when, not if), having my database under source control allows me to recover things quickly.
If you're new to source control in Domino Designer, I have made a video available which walks you through my workflow.
But that's not the point of this post. I have found that when there are 20 or 30 databases each under source control that I spend a lot of my day with Designer hung and displaying this dialog box:
After a cry for help on Twitter, Julian suggested I try turning off automatic sync. I should have known there was a setting for it, but it never occurred to me to look. There are hundreds of configuration settings in Designer preferences, and to be honest I try not to touch them as in my experience they tend to break things more than make them better, but in this case, if you go to Preferences -> Domino Designer -> Source Control and make sure that the "Enable automatic import/export..." options are unchecked then you should find Designer is more usable.
Of course you then have to remember to right click on your database and choose Team Development -> Sync with on disk project to manually force a sync, but that is a habit I can get used to.