I had a bad experience at Guest Relations with our convention tickets that had leftover days on them. My husband still had an extra day from his after 2 pm ticket. His seminar was over at 12 noon each day, and we ended up going directly to the parks, so this type of ticket didn't work well for him. Due to the bad weather we were having, we decided to head home early. We tried to see if we could upgrade the amount left on my children's and husband's tickets to either an AP or some type of park hopper. I was told the first time we checked that we could be refunded the amount left on my husband's tickets (37.50). We did not have all the tickets with us at that time as our kids were at Disney Quest. Later that afternoon a different group of CM's were working in Guest Relations (at DTD), and they refused to do anything with our tickets. We had already decided to check-out of our hotel at that point, so we couldn't stay and use them for the next day or two. I ended up giving them to a family as I was leaving the hotel. At least somebody got some use out of them (I hope!).
I doubt we will ever use the convention type of tickets again, as there are so many restrictions on them, and they were useless once the 10 days were over.