I never knew there was a note limit as such; isn't the internal buffer for midi files about 300k or suchlike?

Anyhow, you could look at it like this: 32000 notes is about 100k worth of a midi file, at a moderately educated guess. It is also 100 notes per second for a 5 minute song.

The biggest (commercial) file I've loaded and run (on my PSR2000) has been 108k so far, and this was crammed with controller and paramater change data, with no problems. I suppose when I hit a problem it will be a straight fail rather than some gradual degradation as the file size approached the limit.

So as long as you stick to fairly normal pop song sequence lengths and do not go totally stupid with the arrangement you should have no problems at all.