It says in the Paid Memberships page that Bishops have the same benefits as Knights. So I'd suspect they also have 20 holidays.
Holidays are reset at January 1st and when the membership is renewed.

So this would mean that it's possible for someone to renew bishop membership every month and so get 20 holidays every month. Which adding up to the 10 weekend days, means that one can go all year long without playing and not timing out either.

I surelly hope I'm wrong!!