My P4 is almost 1,5 years old now. Last weekend the crossfader stopped working.
I mostly play techno and electronic stuff and my workflow doesn’t include any crossfader action. Most of the time it is not used.
Sometines i practice scratches with hip hop beats but really not often maybe 1% of the whole time on the decks.
Those are on minimum 2h daily.
On my device the left side Deck 1/3 is switched open.
I find 1.5 years of non extensive use is not much. My DJM 300 xfader lasted 8 years.
On the other hand i saw one Post where the crossfader was removed and asked if its the original from denon. It was and only 15€ in replacement.
What can i expect from a 15 € xfader? 
The real question is what the hack is a 15€ xf doin in my 1800 € device.
That makes my curious about the lifetime of knobs and linefaders etc.
I feel some knobs and ch 1 and 2 are not tight like they should feel in my honest opinion.
I think about sending it in because of the last half year warranty.
If this would happen in 2 years i would have already ordered an innofader.
What do you guys think of build in fader and knob quality.?
I have to say i love my P4 and my friends too and if denon had said they want 2300€ like it was announced first, i would have also bought it.
Cheers
Rik 