  We take a fresh look at high energy radioactive nuclei data reported in the
90's and at the positron data recently reported by PAMELA. Our aim is to study
the model independent implications of these data for the propagation time
scales of cosmic rays in the Galaxy. Considering radioactive nuclei, using
decaying charge to decayed charge ratios -- the only directly relevant data
available at relativistic energies -- we show that a rigidity independent
residence time is consistent with observations. The data for all nuclei can be
described by f_{s,i}=(t_i/100 Myr)^{0.7}, where f_{s,i} is the suppression of
the flux due to decay and t_i is the observer frame lifetime for nucleus specie
i. Considering positron measurements, we argue that the positron flux is
consistent with a secondary origin. Comparing the positron data with
radioactive nuclei at the same energy range, we derive an upper bound on the
mean electromagnetic energy density traversed by the positrons, \bar U_T<1.25
eV/cm^3 at a rigidity of R=40 GV. Charge ratio measurements within easy reach
of the AMS-02 experiment, most notably a determination of the Cl/Ar ratio
extending up to R\sim100 GV, will constrain the energy dependence of the
positron cooling time. Such constraints can be used to distinguish between
different propagation scenarios, as well as to test the secondary origin
hypothesis for the positrons in detail.
