Since 2^256 is likely a number larger than the number an atoms in the known universe, better get to crackin' with that abacus or wait for the advent of quantum computers if/when machines capable of doing this come to exist in our lifetimes.
2
256 is not the number of the addresses. Even if you brute force private keys, that are around 2
256, you want to find a collision, not necessarily someone's private key. A RIPEMD-160 hash (which is the address decoded) is 160-bits long, which means 2
160. So you're brute forcing this number:
1,461,501,637,330,902,918,203,684,832,716,283,019,655,932,542,976
Since private keys are ~2
256 and all possible combinations of addresses 2
160, then you're trying to find one of the ~2
96 private keys that collide with the same address. So next time you create an address, keep in mind that besides your private key,
there are around 79,228,162,514,264,337,593,543,950,335 more.
do you want to say that beside private key that I am holding for my address there is around this number private keys that will resolve into my address or something else? if that is a fact, I really did not know that, but that does not seems as a good thing, is it?