Honestly the 12-12 TB is ideal. Gives more than sufficient chances to break and leads to potential for classic matches (2008 W F, 2018 W SF, 2019 W F, 2013 FO SF all ended before 12-12 or happened with the 12-12 rule), but cancels out the chance for servebots to play like 8 hour matches. 6-6 is sorta anticlimactic