How can I tell if TempDb is too big?
Could you not simply run sp_spaceused, or a cut down version as you probably don't need both datasets, on tempdb regularly and log the results?
Obviously this will likely result in an underestimate, because it is unlikely that peak space use will be exactly on one of your samples, so you will need to inflate the maximum figures. Perhaps you could use this method to decide a good starting point for the &quot;shrink and watch if it grows back a bit&quot; experiment that you describe.