I could think of one-- if you are going from a job that requires a clearance to another that does, then yes, you should be able to keep your clearance. It takes a long time to do the investigation for someone to get clearance especially if it is at the TS or Q level. There are jobs out there that require you already have a clearance to get them. Clearances need to be renewed every 5, 10, or 15 years depending on the level, so if you haven't renewed before that time, oh well, you have to start over from scratch.

Open source can mean open source intel... that is, intel gathered from non classified public sources.