I helped a friend buy a house at foreclosure for his daughter and SIL. It had hollow core lauan mahogany doors. She wanted them replaced with the paint grade molded six panel doors. Also wanted the bifold closet doors replaced with double swinging doors.
Today I went out there and replaced the nine swinging doors. Turns out the new doors are full width and the old doors were about a 1/4" undersized. I had to dress them down. Turns out the frame inside the doors is so thin/narrow that if you dress all of it off one side, there isn't much left to screw the hinges to. The doors were pre-bored for the locks/door knobs. Can't take much off that side or you lose the setback for the locks.
Then it turns out the openings were not square. Had to dress the doors enough to insert them into the openings and check the fit across the top. That meant cutting enough off the bottom to get them into the openings. If you cut too much off the bottom, you cut the frame off and have to redo it.
The end result of all this is it took me eight hours to hang nine doors. Does that seem reasonable? I felt like I was in slow motion all day. Still got to back and address the three closets.