Dark Matter is essential for structured formation in the late Universe so it must be stable on cosmological time scales. But how stable exactly? Only assuming decays into relativistic on 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-l multipoles of the CMB, the Dark Matter lifetime is expected to correlate with the tensor-to-scalar ratio r as well as the curvature Omega(k.) We consider two model, 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 160 Gyr (without BICEP2) or 200 Gyr (with BICEP2) at 95% confidence level.