Now that the last 10 shifts can be accomplished in roughly 24 hours, it seems to me likely that a shift not paid could scroll off the list. In other words, the work is never paid. Am I thinking about this incorrectly?
Shifts with zero pay happened every once in a while before when 10 shifts were 4x difficulty. Now 10 shifts are 1x difficulty and it will happen more often.
Shifts with zero pay are averaged out by shifts with very high pay. Very high paying shifts also now happen more frequently.
The reduced shift size means no change for 24/7 miners.
The reduced shift size means increased variance for part-time miners.
Also see this:
https://bitcointalk.org/index.php?topic=788753.msg9161208#msg9161208