Becasue non-expiration cost varies with the number of days (originally on and added to) a ticket, we can talk about "the fifth non-expiring day costs x dollars, the sixth non-expiring day costs x dollars and so on". For tickets not used more than 13 days ago you can compute that dollar cost using the prices posted above the ticket booth although several additions and subtractions are needed compared with expiring tickets. If your arithmetic is* above 6'th grade level you are less likely to run into mistakes if you arrive at the number yourself instead of ask the CM to figure it out for you.
For tickets used more than 13 days ago I am not absolutely sure you can add days this way.
For tickets used more than 13 days ago you can still add hopping or water park fun at the prices posted above the ticket booth, last I am told.
(You have to go to Guest Relations, there is also one of these windows outside the turnstiles, to do the upgrade.)
Eeyoreprincess said:
It is non-expiring. I guess I'll have to buy a separate ticket for the remaining days. .
The cost per day is usually much less when you buy a new ticket for the entire vacation when old tickets won't fully cover. For vacations of more than 7 days an expiring ticket usually works best.
Disney hints:
http://members.aol.com/ajaynejr/disney.htm
Don't forget, tickets that have expired are absolutely dead.
*Not was. Everybody's level in all subjects goes down without practice as years go by since graduation.