I absolutely love the dungeon themes from these two games, but my only gripe is that most of the rips out there are relatively short and it really disrupts the mood / flow / ambiance to have to play it again from start. I have been hard pressed to find rips that go on for longer than 2:00 or so (although I did find one version of the Fire Temple that goes on for about 5:00).

Does anyone know if such files already exist and where I can find them?

Go here:
http://zeldapower.com/index.php/downloads/music_&_soundtracks/ocarina_of_time_dungeon_tracks.php

If you go back by one option on the site, there is a ton of other Zelda music available. These are for Ocarina of Time's dungeons.

Great site, thanks!