I recently noted that mass, gravity and time may be essential features – givens – of our universe, that gravity is something that slows time and that at the speed of light, time stops. Actually time doesn't stop at the speed of light but becomes instantaneous. At that speed, everything happens at once. It's at an event horizon that time actually just stops passing. As whatever it is that is “falling” into a black hole passes the event horizon, the time that it may be experiencing cannot escape. Beyond that, at the singularity, anything/everything disappears from this universe (leaving aside the mechanism by which black holes “evaporate” over time). The mass and energy falling into the singularity is converted into the very warping of space that is the black hole.
How long does it take to fall from the event horizon into the singularity? Has time there stopped or has it become instantaneous? Apparently, if you could survive passing through the event horizon, you would still experience your own personal time. The length of time you'd experience would be very short but it would pass. As under general relativity there is no absolute standard of time, that would be all that counts for you. Indeed, time may be thought of as something entirely a matter of perspective. As I would be falling through the event horizon experiencing my own usual passage of time – it would not slow down or stop – it would appear to be doing so only to an outside observer experiencing his own usual passage of time.
Our human sense of the passage of time may be an entirely arbitrary experience defined by our nature as biological mechanisms (with mass) operating according to physical laws as elaborated by the evolution of life on our particular planet. One defining process may be the rate at which ribosomes add amino acids to the protein it is building (called translation). In all life on earth this process proceeds at the same speed of 10-20 additions per second. A “second” is a human unit of time but not an entirely arbitrary one as at the most fundamental level it is related to two apparent givens: the ability of our consciousness to hold just 2-3 seconds as our now and the existence of a basic unit – the Planck time – of 5.39x10 to the -44th seconds. Or perhaps we might simply say that our human, species experience of time is one heart beat. That, however, might speed up a bit as we crossed the horizon.