Hi Ian

no max length in terms of movie playback

HOWEVER:
In and out frame are only possible for 65535 frames(16bit - about 42mins at 25fps) - but this does not limit playback to 42 mins - movies will run longer, but you cant specify the in/out point beyond 655535 frames... fine for most scenarios

This also provides an issue for sync to smpte for the same 65535 reasons. Richard did introduce a feature of adding both inframe and outframe values to allow smpte sync over 65535 frames. However, Catalyst ignores the "hours" for smpte timecode - so it can still cause issues if your clip is over an hour long, or starts near an hour change...

There is the ability to introduce an offset - but this can get VERY complicated...

In short - sync to smpte for movies less than 42 mins (@25fps) works fine... you will need to experiment for syncing longer movies.

Simon