What happens if a team returns a blocked extra point a long way, but not all the way to the end zone?
The ball is considered dead, and the rules regarding what takes place after a try (a kickoff) is put into effect.
As posted here, an extra point is defined as a "try."
A specific rule reference for the NCAA regarding the results of a try can be found at Rule 8, Section 3, Article 2 (specifically point d2):
d. The try ends when:
- The ball is dead by rule (A.R. 8-3-2-IV and VI).
A specific rule reference for the NCAA regarding what takes place after a try can be found at Rule 8, Section 3, Article 6:
After a try, the ball shall be put in play by a kickoff or at the
succeeding spot in extra periods. The team scoring the six-point touchdown
shall kick off.
A specific rule reference for the NFL regarding the results of a try can be found at Rule 11, Section 3, Article 2 (specifically point e):
During a Try, the following shall apply:
(e) The Try ends when ... the ball is dead by rule.
A specific rule reference for the NFL regarding what takes place after a try can be found at Rule 3, Section 18, Article 5, Item 1:
A Kickoff is a kick that puts the ball in play at the start of each
half, at the start of overtime, after each Try, and after a successful
field goal.