Depent of your speed, i made some calculations based on the speed, the time is for scan all the range in that bit space:
Puzzle 120 @ 1 Petakeys/s : 21074771622667 years
Puzzle 120 @ 1 Exakeys/s : 21074771622 years
Puzzle 120 @ 1 Zettakeys/s : 21074771 years
Puzzle 120 @ 1 Yottakeys/s : 21074 years
Puzzle 160 @ 1 Terakeys/s : 23171956451847141650870193314 years
Puzzle 160 @ 1 Petakeys/s : 23171956451847141650870193 years
Puzzle 160 @ 1 Exakeys/s : 23171956451847141650870 years
Puzzle 160 @ 1 Zettakeys/s : 23171956451847141650 years
Puzzle 160 @ 1 Yottakeys/s : 23171956451847141 years
Puzzle 256 @ 1 Terakeys/s : 1835871531540401373407708412745559168131740612197318060720 years
Puzzle 256 @ 1 Petakeys/s : 1835871531540401373407708412745559168131740612197318060 years
Puzzle 256 @ 1 Exakeys/s : 1835871531540401373407708412745559168131740612197318 years
Puzzle 256 @ 1 Zettakeys/s : 1835871531540401373407708412745559168131740612197 years
Puzzle 256 @ 1 Yottakeys/s : 1835871531540401373407708412745559168131740612 years
I know there is no puzzle 256, but that is the exact time for the real wallets.
(2^ 60 too high)
I also implement BSGS in C, in my tool Keyhunt, is not so fast, but the puzzle 63 can be solved in one hour or two. Also in minutes is you have some luck with Random mode.
Puzzles without publickey are more slow, that is why puzzle 64 is stll not found.
Regards!
I use my old GTX 960 and it literally solve 63 in less than a minute. If I want to use it to hunt 120, average 300 years. LoL. I guess if 64 with known public key and I use GTX 3060, I guess it can be solve in less than 15 seconds. That's also reason why if by chance you found 64, someone recommend to pay higher on transaction fees or otherwise once known public key, I believe those bot will attack in less than a minute.