I'd like to take this opportunity to also vent about the 24th fret intonation check. (please don't flame me) I've heard some guys advocate it, and I understand why. But first off, many times the fret location is a bit off by the time you get up there. And the slightest difference in fret crown or fret placement can throw the reading off-more "off" than at the 12th for example. Also, I am more interested in chords from fret 1-12 sounding in tune with eachother, than if my wailing solo (with vibrato by the way) above the 12th fret is a little off. If you make 3-4 note chords up there past the 15th I appologize. But I sure don't. If I do it's funky scratchy stuff that's more about percussion and dissonance than about long smooth chords.
Also, you have to intonate your own guitars to match your squeeze pressure IMO. If you dig into the strings and pull them sharp against jumbo frets, you have to intonate a little flat or better yet, intonate in playing position using your technique. If you have a light touch, you can intonate a little more precisely. When doing guitars for customers I just intonate "mathematically." That is, simply apply enough pressure to properly fret the note, and no more. Also I notice some players attack the strings going forward. That can push a note flat. The opposite is also true. That is much more noticeable on the higher frets. You can get the 24th fret to match the harmonic on the tuner just by how you hold the note down!