Got to admit I've never had a good concept of ageing with respect to speed. I can imagine a change in ageing when there is a speed differential, but once any two objects become adjacent again, say two atomic clocks, everything about relativity suggests they should show the same time again. If that weren't true then somehow relativity would be asymmetric, not conserved and/or there would necessarily be an absolute reference against which time dilation occurs, like what you are suggesting.