I have a 2003 Honda Civic Hybrid. The transmission startead slipping at about 40,000 miles. I took it to the Honda Dealer and they recommended changing the transmission fluid which I did. It started slipping again about 5,000 miles later. I changed it again (each time it cost me $100 plus fluid).
that seemed to fix it for a long time. At about 100,000 miles I noticed it slipping again. I was on my way home from N.Y. When I got home I had a letter saying the warranty was extended to 100,000 miles. I called them and they asked for the milage. It was 100,450 (or thereabouts). They said it was beyond the exteded warranty mileage and refused to fix it.
Since that time I have changed the transmission oil twice and it still slips.