Since questions are auto-CW-ed on their 30th answer, it would probably be nice to make sure this does not happen because of 10 "thank you" answers but due to real answers that actually justify the CW-ing
I propose a different solution.
There's a very good possibility that a question on the Stack Exchange network should not have 30 answers in the first place. If a question has 30 answers it most likely fits into one of the following categories:
Only the first is worthy of a protected status, the other two should be closed and/or deleted.
After the 25th answer an automatic
If the question is in need of the protection status, it will be cleaned up at the same time and protected afterwards. If it is something which should be closed/deleted, this will also happen.