I made the WS for the first time in a long time but forgot how many pitchers I carried. During my playoff run in the NL I carried 11 pitchers and never encountered a problem with too many tired pitchers but my extra hitter only had 1AB. I don't have a lot of high durability pitchers and I'm worried that I may get into some trouble with high pitch count games on the road. Do I keep my extra hitter who is a VL specialist and a good PR or add a 12th pitcher?

With all the off-days in the post-season, I can't see any reason to need 12 pitchers.

I'd go with the extra bench player . . . PH bat, defensive specialist, or PR.

Say it twice!!

You probably only need 9 pitchers.   I used 10 on my two WS winners.   I had pitchers on the staff throw 2 and 3 innings in the entire post-season.

In the NL you definitely need the extra hitter in the playoffs.  Pinch hitter/runner, defensive replacement.  Then again, I make very VERY generous usage of my bench.  In a typical NL game, I usually get all 13 batters into the game somehow someway.  I've made 3 consecutive deep post season runs, and like miket, I've had multiple pitchers go 2 innings or less the whole postseason.  I go with a 3-man rotation, 4th starter is now SUA, 5th starter is LRA, LRA is now LRB, my worst SUA is now SUB, then I have 2 regular SUA (both low stamina high durability) and a closer who is low stamina low durability. 

I use 3 SP, 3 LR, 3 short men.   If I'm not mistaken, the guys who got less than 3 innings were the 33/12 DUR/STM guys who are good for 10 pitches every 3rd day.  They usually have the great splits/pitches but are hard to carry during the season because they're giving you 35 innings.