There is keen competition to produce the largest pair of twin primes.
On October 9, 1995, Dubner discovered the largest known pair of twin
primes p,p+2 where p=570918348*10^5120 - 1. It took only one day
with 2 crunchers. The expected time would be 150 times longer! What
luck!
-- from P. Ribenboim,
'The new book of prime number records'