  We study time averages for the norm of solutions to kinetic Fokker--Planck
equations associated with general Hamiltonians. We provide fully explicit and
constructive decay estimates for systems subject to a confining potential,
allowing fat-tail, sub-exponential and (super-)exponential local equilibria,
which also include the classic Maxwellian case. The key step in our estimates
is a modified Poincar\'e inequality, obtained via a Lions--Poincar\'e
inequality and an averaging lemma.
