The current SoB challenge has very long WU times. My i7-4590k takes 2 days 14 h to complete and therefore will manage to complete 3 WUs, meaning I can stop the challenge after 9 of 10 days, leaving one "dead day". My i3-2110 needs more than 5 days, i.e. after halftime I can already remove it from the challenge. I guess many people will run into similar problems.
Simply extending the challenge duration obviously doesn't help.
So what do you think about introducing a grace period within which WUs can still be reported if they were started within the challenge, but WUs started within that grace period are invalid no matter when they finish.
For SoB this period could be set to 2 days, that would decrease the number of "dead days" strongly. Only computers that take more than 6 days would be left with 4 "dead days".
I know this will be a slight disadvantage for fast computers, because they don't need that period. Overall I think it will help increase participation greatly.
Primes: 1281979 & 12+8+1979 & 1+2+8+1+9+7+9 & 1^2+2^2+8^2+1^2+9^2+7^2+9^2 & 12*8+19*79 & 12^8-1979 & 1281979 + 4 (cousin prime)