This has already been discussed earlier. The length of the protein is NOT necessarily an indication of how long it will take. And the proteins will NOT keep getting longer and longer indefinitely. They will vary in size, especially for CASP. 180 is on the border of what is currently "worth trying" with the present approach. Anything bigger would produce such terrible structures that they wouldn't be worth submitting to CASP. Of course we may not need to solve those proteins by brute force always..
Anyways, it will all balance out in the end and the scoring will not be touched in that respect.