hey, well ive been playing my schecter omen for almost 1 and a half years now and i was wondering why i have trouble hitting, and sustaining notes higher then the 17th fret
put some vibrato if you hit it right

and try to hit it right behind the fret, not in the middle between the frets
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Im guessing this is a recent problem. Try cleaning your fretboard with lemon oil next time you take off your strings, as grime will really hurt your overall sustain. Just make sure that all parts of your guitar are very clean, and that your strings are fairly new. Also vibrato helps to sustain the notes.
thnx for the recent feeback but yah i think the last guys right ive always had problems with this since i got it and i change my strings a lot, but im prolly getting an ibanez soon so thnx anyway