My laptop, running an i7-4XXX can hit about 1 millions keys per second using a vanity address generator at its peak. This usually slows down as it heats up, and it is certainly possible to go faster with GPUs.
Assuming the strongest hardware today is 10000x faster, or can generate 10 billion keys per second, you will reach 10^18 in 10^18/10^10 seconds, which is 1157 days.
Note that the Bitcoin keyspace is much larger, about 2^256 (although I believe you "only" need to crack 2^128 to start breaking into stuff with high probability, but I can't find that reference right now). For 2^256 keys, even at 10 billion per second, it would take you 3.672×10^59 years, which is 2.7×10^49 times the age of the universe.
Edit:
You would only need to go through 2^160 combinations to break a p2pkh address, since you only need to beat the HASH160. This reduces your time to only 4.631×10^30 years.
Why 10^18? I can't see any logic or significance to that number – Raghav Sood – 2018-08-07T15:54:37.907
@RaghavSood it about amount of 64bits possible passwords combinations, lowest form of security for cryptocurrency i found, so this number might suitable to try – Huang Lee – 2018-08-07T15:58:01.810
2^64 is still about 18.5x larger than 10^18 – Raghav Sood – 2018-08-07T16:13:02.757
"Strongest hardware" is kind of impossible to define since this task is totally parallelizable. Whatever hardware you have in mind, just get two of them, and then you'll finish the job in half the time. – Nate Eldredge – 2018-08-07T16:25:18.380