Assuming they are compatible and your tank is big enough, yes. If you are starting a tank and trying to stock it, you are almost forced to, since you couldn't add fish any faster than 1 every 6-8 weeks otherwise, depending on how long your quarantine for and how long you let your QT sit empty.
As mentioned above, the down side is if one develops any symptoms, you're obligated to treat both for the duration. Even though you expose the 'healthy' fish to the sick fish, you still prevent the exposure to your DT.