  This paper presents a detailed investigation of the dependence of pulsar
spin-velocity alignment, which has been observed for a sample of 58 pulsars, on
pulsar age. At first, our study considers only pulsar characteristic ages,
resulting in no change in the degree of correlation as a function of age, up to
at least 100 Myr. Subsequently, we consider a more reliable estimate of pulsar
age, the kinematic age, assuming that pulsars are born near the Galactic plane.
We derive kinematic ages for 52 pulsars, based on the measured pulsar proper
motions and positions, by modelling the trajectory of the pulsars in a Galactic
potential. The sample of 52 pulsar kinematic ages constitutes the largest
number of independently estimated pulsar ages to date. Using only the 33 most
reliable kinematic ages from our simulations, we revisit the evolution of spin-
velocity alignment, this time as a function of kinematic age. We find that the
strong correlation seen in young pulsars is completely smeared out for pulsars
with kinematic ages above 10 Myr, a length of time beyond which we expect the
gravitational pull of the Galaxy to have a significant effect on the directions
of pulsar velocities. In the discussion, we investigate the impact of large
distance uncertainties on the reliability of the calculated kinematic ages.
Furthermore, we present a detailed investigation of the implications of our
revised pulsar ages for the braking-index and birth-period distributions.
Finally, we discuss the predictions of various SN-kick mechanisms and their
compatibility with our results.
