  We consider a particle dragged through a medium at constant temperature as
described by a Langevin equation with a time-dependent potential. The
time-dependence is specified by an external protocol. We give conditions on
potential and protocol under which the dissipative work satisfies an exact
symmetry in its fluctuations for all times. We also present counter examples to
that exact fluctuation symmetry when our conditions are not satisfied. Finally,
we consider the dissipated heat which differs from the work by a temporal
boundary term. We explain when and why there can be a correction to the
standard fluctuation theorem due to the unboundedness of that temporal
boundary. However, the corrected fluctuation symmetry has again a general
validity.
