Image from The City University of New York
Too much is made of the fact that Hawking Radiation leads to the conclusion that black holes will not exist forever in pop-sci culture. The seemingly "mind blowing" idea that a black hole would "evaporate" someday is too often presented as if a black hole is some incredibly shrinking object that is inherently unstable. Nothing could be farther from the truth.
Let's put it into a little perspective:
A proton is considered one of the most stable composite particles in the universe. The proton has a half-life of at least 10^34 years. Proton decay is so rare that it has NEVER been observed. However, if the theoretical approximations of the proton is correct, almost ALL protons will have decayed after 100 half-lives, or 10^36 years. That is a LONG time from now! (Note: Although, neutrons will ALSO be decaying during this time, so new protons will be created and it could take another 10^36 years. However, 2x10^36 is very close to 10^36 in the exponential scales we are looking at.)
How does this compare to the decay of a black hole with the mass of the Sun?
A solar mass black hole would take 10^64 years to evaporate. That is MUCH longer than the complete evaporation time of ALL protons in the universe. In fact it is 10^28 TIMES LONGER!!! In other words, during the lifetime of a small 1 solar mass black hole, every proton in the universe could decay away, more protons could come into existence, then THOSE could decay away and this could happen 10^28 times over!!!
That is such a VASTLY longer time than the time than the already VERY LONG time protons exist, so much so that the lifetime of a proton is a smaller portion of the lifetime of a black hole than 40 pico-seconds (4x10^-11 seconds) is to the ENTIRE LIFETIME OF THE UNIVERSE! (If that doesn't blow your mind a little bit you need to read that sentence again.)
Larger black holes have an every LONGER lifetime. While our own galaxy's supermassive black hole, Sagittarius A*, has a mass of "only" 4x10^6 solar masses, other super-massive black holes have much larger masses. A supermassive black hole with 10^11 solar masses will evaporate in around 2×10^100 years![Wikipedia]
It is impossible to even fathom what the universe will look like by the time black holes get anywhere CLOSE to evaporating. For instance, it's possible that the Higss field itself will have decayed away from the expansion of spacetime and electrons and quarks will loose their rest mass altogether; then all matter in the universe will be dissipated! In other words, we simply can't even start to predict what will happen at those timescales.
So I wish people would STOP focusing so much on the fact that black holes will evaporate some day. The insanely vast amount of time that it will take for black holes to "evaporate" doesn't even make any sense to our brains.
Black holes are some of the most stable and long-lived objects in the known universe. Just because we can write down a number of years when they may "evaporate" doesn't change this fact.
