Ok. When you say 'how fast an object moves through time', you mean 'how fast time passes for a moving object, as seen from the inertial reference frame of another object'.
I regard objects as moving at the same speed through time - 1 second per second.
It's of course a matter of taste what expression sounds more fitting to you, precisely because time is such a fluid concept.
Personally, when I think about a neutrino for example, I'd say that neutrinos go crazy fast, and they experience time unimaginably slowly, so it feels more natural for me to think that velocity and time are tradeoff values of each other.
I regard objects as moving at the same speed through time - 1 second per second.