  Using available data for C and M giants with Mbol<-3.6 in Magellanic Cloud
clusters, we derive limits to the lifetimes of the corresponding evolutionary
phases, as a function of stellar mass. The C-star phase is found to have a
duration between 2 and 3 Myr for stars in the mass range from 1.5 to 2.8 Msun.
There is also an indication that the peak of C-star lifetime shifts to lower
masses (from slightly above to slightly below 2 Msun) as we move from LMC to
SMC metallicities. The M-giant lifetimes also peak at 2 Msun in the LMC, with a
maximum value of about 4 Myr, whereas in the SMC their lifetimes appear much
shorter but, actually, they are poorly constrained by the data. These numbers
constitute useful constraints to theoretical models of the TP-AGB phase. We
show that several models in the literature underestimate the duration of the
C-star phase at LMC metallicities.
