  Dark Matter is essential for structure formation in the late Universe so it
must be stable on cosmological time scales. But how stable exactly? Only
assuming decays into relativistic particles, we report an otherwise model
independent bound on the lifetime of Dark Matter using current cosmological
data. Since these decays affect only the low-$\ell$ multipoles of the CMB, the
Dark Matter lifetime is expected to correlate with the tensor-to-scalar ratio
$r$ as well as curvature $\Omega_k$. We consider two models, including $r$ and
$r+\Omega_k$ respectively, versus data from Planck, WMAP, WiggleZ and Baryon
Acoustic Oscillations, with or without the BICEP2 data (if interpreted in terms
of primordial gravitational waves). This results in a lower bound on the
lifetime of CDM given by 160Gyr (without BICEP2) or 200Gyr (with BICEP2) at 95%
confidence level.
