We measure the total-mass-density profiles out to three effective radii for a sample of 63 z similar to 0.5, massive early-type galaxies (ETGs) acting as strong gravitational lenses through a joint analysis of lensing and stellar dynamics. The compilation is selected from three galaxy-scale strong-lens samples, namely the Baryon Oscillation Spectroscopic Survey (BOSS) Emission-Line Lens Survey (BELLS), the BELLS for GALaxy-Ly alpha EmitteR sYstems Survey (BELLS GALLERY), and the Strong Lensing Legacy Survey (SL2S). Utilizing the wide source-redshift coverage (0.8-3.5) provided by these three samples, we build a statistically significant ensemble of massive ETGs for which robust mass measurements can be achieved within a broad range of Einstein radii up to three effective radii. Characterizing the three-dimensional total-mass-density distribution by a power-law profile as rho proportional to r(-gamma), we find that the average logarithmic density slope for the entire sample is = 2.000(-0.032)(+0.033) (68 per cent CL) with an intrinsic scatter of delta = 0.180(-0.028)(+0.032). Further parametrizing gamma as a function of redshift z and the ratio of Einstein radius to effective radius R-ein/R-eff, we find that the average density distributions of these massive ETGs become steeper at later cosmic times and at larger radii, with magnitudes d /dz = -0.309(-0.160)(+0.166) and d /d log(10)(R-ein/R-eff) = 0.194(-0.083)(+0.092).