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I've not got figures to hand, but it's incredibly slow. They are effectively perfect black body radiators, with their apparent temperature linked to their mass. The bigger they are, the colder they are.
Some back of the envelope calculations.
Right now, they are considerably colder than the cosmic background radiation, and so losses to hawking radiation are overwhelmed by even this. I just did a quick calculation on the milk way supermassive black hole, and it's about 1.5x10^-16 °C. That would work out as around 3x10^-91W/m^2 or around 1x10^-71W. It's about 1x10^13 Joules per gram of matter. So you're looking at 10^84 seconds. The universe is about 4.4x10^16 seconds old, so around 10^68 times the current age of the universe.
To emit 1g will take around 100000000000000000000000000000000000000000000000000000000000000000000 x the age of the current universe. This ignores infalling energy.
It seems like a ridiculously huge amount of time for such a small amount, more so considering that according to theory these black holes will eventually evaporate completely.
But then I try and visualize just how much it actually takes to go from 10^99 to hit the 10^100 (googol) milestone, and it's just too big a numerical chasm to truly wrap one's mind around. It all reaches the level of bizarre abstractions way, way, waaaay before that point.
Something I like to think about is when we die, assuming there's no afterlife, then you don't feel the passage of time. A second or trillion of years is the same. If there's ever a point in that future where you'd gain consciousness again somehow, then you'd feel as if you'd be there the second after you died. It doesn't really relate to black holes but I felt like sharing the thought anyway.
The boltzmann brain hypothesis. Given enough time, a spontaneous brain, identical to yours, will form. It will experience for a short period before dying (nothing says it needs to be on a planet, or even in a body).
The weirdness of true infinities.
Wouldn't that be considered afterlife too?
Well if time is infinite, isn't it only a matter of time until your brain is somehow reassembled