For the majority of applications, a shuttered version of OEM camera is the best option.
All uncooled microbolometer-based cameras drift with temperature changes, and for optimum image quality the pixels occasionally need to be re-normalized. This process is called a Flat Field Correction, or FFC. The parameters for FFC are time and temperature change.
The shuttered versions of FLIR`s OEM cameras perform this operation automatically, however the user has some control over the frequency of FFC by way of setting the amount of time between shuttering, and/or the amount that the ambient temperature can change before shuttering.
In certain situations where the scene or the system is always moving, a non-shuttered version can be used, as FLIR`s OEM cameras employ sophisticated software that will compensate for this drift. However, an initial FFC should be performed using a uniform object or source in front of the lens (even a hand in front of the lens will work).
Without details of the intended end-use of the camera or system, FLIR`s guidance is to specify a shuttered version of OEM camera.